Hey! In our past we had a couple of discussions about whether we should or should not use Optionals [1][2]. The main argument against it was performance. On one hand we risk additional object allocation (the Optional itself) and wrong inlining decisions taken by C2 compiler [3]. On the other hand we all probably "feel" that both of those things shouldn't be a problem and should be optimized by C2. Another argument was the Optional's doesn't give us anything but as I checked, we introduced nearly 80 NullPointerException bugs in two years [4]. So we might consider Optional as a way of fighting those things. The final argument that I've seen was about lack of higher order functions which is simply not true since we have #map, #filter and #flatmap functions. You can do pretty amazing things with this. I decided to check the performance when refactoring REST interface. I created a PR with Optionals [5], ran performance tests, removed all Optionals and reran tests. You will be surprised by the results [6]: Test case With Optionals [%] Without Optionals Run 1 <http://perfrepo.mw.lab.eng.bos.redhat.com/reports/tableComparisonReport/5... Run 2 <http://perfrepo.mw.lab.eng.bos.redhat.com/reports/tableComparisonReport/5... Avg Run 1 <http://perfrepo.mw.lab.eng.bos.redhat.com/reports/tableComparisonReport/5... Run 2 <http://perfrepo.mw.lab.eng.bos.redhat.com/reports/tableComparisonReport/5... Avg Non-TX reads 10 threads Throughput 32.54 32.87 32.71 31.74 34.04 32.89 Response time -24.12 -24.63 -24.38 -24.37 -25.69 -25.03 Non-TX reads 100 threads Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 Response time -6.15 14.93 4.39 7.88 6.49 7.19 Non-TX writes 10 threads Throughput 9.21 7.60 8.41 4.66 7.15 5.91 Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 Non-TX writes 100 threads Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 I also created JMH + Flight Recorder tests and again, the results showed no evidence of slow down caused by Optionals [7]. Now please take those results with a grain of salt since they tend to drift by a factor of +/-5% (sometimes even more). *But it's very clear the performance results are very similar if not the same.* Having those numbers at hand, do we want to have Optionals in Infinispan codebase or not? And if not, let's state it very clearly (and write it into contributing guide), it's because we don't like them. Not because of performance. Thanks, Sebastian [1] http://lists.jboss.org/pipermail/infinispan-dev/2017-March/017370.html [2] http://lists.jboss.org/pipermail/infinispan-dev/2016- August/016796.html [3] http://vanillajava.blogspot.ro/2015/01/java- lambdas-and-low-latency.html [4] https://issues.jboss.org/issues/?jql=project%20%3D% 20ISPN%20AND%20issuetype%20%3D%20Bug%20AND%20text%20%7E% 20%22NullPointerException%22%20AND%20created%20%3E%3D% 202015-04-27%20AND%20created%20%3C%3D%202017-04-27 [5] https://github.com/infinispan/infinispan/pull/5094 [6] https://docs.google.com/a/redhat.com/spreadsheets/d/ 1oep6Was0FfvHdqBCwpCFIqcPfJZ5-5_YYUqlRtUxEkM/edit?usp=sharing [7] https://github.com/infinispan/infinispan/pull/ 5094#issuecomment-296970673 -- SEBASTIAN ŁASKAWIEC INFINISPAN DEVELOPER Red Hat EMEA <https://www.redhat.com/> <https://red.ht/sig> _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev

I think Sanne's right here, any differences in such large scale test are hard to decipher. Also, as mentioned in a previous email, my view on its usage is same as Sanne's: * Definitely in APIs/SPIs. * Be gentle with it internals. Cheers, -- Galder Zamarreño Infinispan, Red Hat > On 18 May 2017, at 14:35, Sanne Grinovero <sanne(a)infinispan.org&gt; wrote: > > Hi Sebastian, > > sorry but I think you've been wasting time, I hope it was fun :) This is not the right methodology to "settle" the matter (unless you want Radim's eyes to get bloody..). > > Any change in such a complex system will only affect the performance metrics if you're actually addressing the dominant bottleneck. In some cases it might be CPU, like if your system is at 90%+ CPU then it's likely that reviewing the code to use less CPU would be beneficial; but even that can be counter-productive, for example if you're having contention caused by optimistic locking and you fail to address that while making something else "faster" the performance loss on the optimistic lock might become asymptotic. > > A good reason to avoid excessive usage of Optional (and *excessive* doesn't mean a couple dozen in a millions lines of code..) is to not run out of eden space, especially for all the code running in interpreted mode. > > In your case you've been benchmarking a hugely complex beast, not least over REST! When running the REST Server I doubt that allocation in eden is your main problem. You just happened to have a couple Optionals on your path; sure performance changed but there's no enough data in this way to figure out what exactly happened: > - did it change at all or was it just because of a lucky optimisation? (The JIT will always optimise stuff differently even when re-running the same code) > - did the overall picture improve because this code became much *less* slower? > > The real complexity in benchmarking is to accurately understand why it changed; this should also tell you why it didn't change more, or less.. > > To be fair I actually agree that it's very likely that C2 can make any performance penalty disappear.. that's totally possible, although it's unlikely to be faster than just reading the field (assuming we don't need to do branching because of null-checks but C2 can optimise that as well). > Still this requires the code to be optimised by JIT first, so it won't prevent us from creating a gazillion of instances if we abuse its usage irresponsibly. Fighting internal NPEs is a matter of writing better code; I'm not against some "Optional" being strategically placed but I believe it's much nicer for most internal code to just avoid null, use "final", and initialize things aggressively. > > Sure use Optional where it makes sense, probably most on APIs and SPIs, but please don't go overboard with it in internals. That's all I said in the original debate. > > In case you want to benchmark the impact of Optional make a JMH based microbenchmark - that's interesting to see what C2 is capable of - but even so that's not going to tell you much on the impact it would have to patch thousands of code all around Infinispan. And it will need some peer review before it can tell you anything at all ;) > > It's actually a very challenging topic, as we produce libraries meant for "anyone to use" and don't get to set the hardware specification requirements it's hard to predict if we should optimise the system for this/that resource consumption. Some people will have plenty of CPU and have problems with us needing too much memory, some others will have the opposite.. the real challenge is in making internals "elastic" to such factors and adaptable without making it too hard to tune. > > Thanks, > Sanne > > > > On 18 May 2017 at 12:30, Sebastian Laskawiec <slaskawi(a)redhat.com&gt; wrote: > Hey! > > In our past we had a couple of discussions about whether we should or should not use Optionals [1][2]. The main argument against it was performance. > > On one hand we risk additional object allocation (the Optional itself) and wrong inlining decisions taken by C2 compiler [3]. On the other hand we all probably "feel" that both of those things shouldn't be a problem and should be optimized by C2. Another argument was the Optional's doesn't give us anything but as I checked, we introduced nearly 80 NullPointerException bugs in two years [4]. So we might consider Optional as a way of fighting those things. The final argument that I've seen was about lack of higher order functions which is simply not true since we have #map, #filter and #flatmap functions. You can do pretty amazing things with this. > > I decided to check the performance when refactoring REST interface. I created a PR with Optionals [5], ran performance tests, removed all Optionals and reran tests. You will be surprised by the results [6]: > > Test case > With Optionals [%] Without Optionals > Run 1 Run 2 Avg Run 1 Run 2 Avg > Non-TX reads 10 threads > Throughput 32.54 32.87 32.71 31.74 34.04 32.89 > Response time -24.12 -24.63 -24.38 -24.37 -25.69 -25.03 > Non-TX reads 100 threads > Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 > Response time -6.15 14.93 4.39 7.88 6.49 7.19 > Non-TX writes 10 threads > Throughput 9.21 7.60 8.41 4.66 7.15 5.91 > Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 > Non-TX writes 100 threads > Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 > Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 > > I also created JMH + Flight Recorder tests and again, the results showed no evidence of slow down caused by Optionals [7]. > > Now please take those results with a grain of salt since they tend to drift by a factor of +/-5% (sometimes even more). But it's very clear the performance results are very similar if not the same. > > Having those numbers at hand, do we want to have Optionals in Infinispan codebase or not? And if not, let's state it very clearly (and write it into contributing guide), it's because we don't like them. Not because of performance. > > Thanks, > Sebastian > > [1] http://lists.jboss.org/pipermail/infinispan-dev/2017-March/017370.html > [2] http://lists.jboss.org/pipermail/infinispan-dev/2016-August/016796.html > [3] http://vanillajava.blogspot.ro/2015/01/java-lambdas-and-low-latency.html > [4] https://issues.jboss.org/issues/?jql=project%20%3D%20ISPN%20AND%20issuety... > [5] https://github.com/infinispan/infinispan/pull/5094 > [6] https://docs.google.com/a/redhat.com/spreadsheets/d/1oep6Was0FfvHdqBCwpCF... > [7] https://github.com/infinispan/infinispan/pull/5094#issuecomment-296970673 > -- > SEBASTIAN ŁASKAWIEC > INFINISPAN DEVELOPER > Red Hat EMEA > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev

I wouldn't say I'm an extreme naysayer, but I do have 2 issues with Optional: 1. Performance becomes harder to quantify: the allocations may or may not be eliminated, and a change in one part of the code may change how allocations are eliminated in a completely different part of the code. 2. My personal opinion is it's just ugly... instead of having one field that could be null or non-null, you now have a field that could be null, Optional.empty(), or Optional.of(something). Cheers Dan On Tue, May 23, 2017 at 1:54 PM, Sebastian Laskawiec <slaskawi(a)redhat.com&gt; wrote: > Hey! > > So I think we have no extreme naysayers to Optional. So let me try to sum > up what we have achieved so: > > - In macroscale benchmark based on REST interface using Optionals > didn't lower the performance. > - +1 for using it in public APIs, especially for those using > functional style. > - Creating lots of Optional instances might add some pressure on GC, > so we need to be careful when using them in hot code paths. In such cases > it is required to run a micro scale benchamark to make sure the performance > didn't drop. The microbenchmark should also be followed by macro scale > benchamrk - PerfJobAck. Also, keep an eye on Eden space in such cases. > > If you agree with me, and there are no hard evidence that using Optional > degrade performance significantly, I would like to issue a pull request and > put those findings into contributing guide [1]. > > Thanks, > Sebastian > > [1] https://github.com/infinispan/infinispan/tree/master/ > documentation/src/main/asciidoc/contributing > > On Mon, May 22, 2017 at 6:36 PM Galder Zamarreño <galder(a)redhat.com&gt; > wrote: > >> I think Sanne's right here, any differences in such large scale test are >> hard to decipher. >> >> Also, as mentioned in a previous email, my view on its usage is same as >> Sanne's: >> >> * Definitely in APIs/SPIs. >> * Be gentle with it internals. >> >> Cheers, >> -- >> Galder Zamarreño >> Infinispan, Red Hat >> >> > On 18 May 2017, at 14:35, Sanne Grinovero <sanne(a)infinispan.org&gt; >> wrote: >> > >> > Hi Sebastian, >> > >> > sorry but I think you've been wasting time, I hope it was fun :) This >> is not the right methodology to "settle" the matter (unless you want >> Radim's eyes to get bloody..). >> > >> > Any change in such a complex system will only affect the performance >> metrics if you're actually addressing the dominant bottleneck. In some >> cases it might be CPU, like if your system is at 90%+ CPU then it's likely >> that reviewing the code to use less CPU would be beneficial; but even that >> can be counter-productive, for example if you're having contention caused >> by optimistic locking and you fail to address that while making something >> else "faster" the performance loss on the optimistic lock might become >> asymptotic. >> > >> > A good reason to avoid excessive usage of Optional (and *excessive* >> doesn't mean a couple dozen in a millions lines of code..) is to not run >> out of eden space, especially for all the code running in interpreted mode. >> > >> > In your case you've been benchmarking a hugely complex beast, not >> least over REST! When running the REST Server I doubt that allocation in >> eden is your main problem. You just happened to have a couple Optionals on >> your path; sure performance changed but there's no enough data in this way >> to figure out what exactly happened: >> > - did it change at all or was it just because of a lucky >> optimisation? (The JIT will always optimise stuff differently even when >> re-running the same code) >> > - did the overall picture improve because this code became much >> *less* slower? >> > >> > The real complexity in benchmarking is to accurately understand why it >> changed; this should also tell you why it didn't change more, or less.. >> > >> > To be fair I actually agree that it's very likely that C2 can make any >> performance penalty disappear.. that's totally possible, although it's >> unlikely to be faster than just reading the field (assuming we don't need >> to do branching because of null-checks but C2 can optimise that as well). >> > Still this requires the code to be optimised by JIT first, so it won't >> prevent us from creating a gazillion of instances if we abuse its usage >> irresponsibly. Fighting internal NPEs is a matter of writing better code; >> I'm not against some "Optional" being strategically placed but I believe >> it's much nicer for most internal code to just avoid null, use "final", and >> initialize things aggressively. >> > >> > Sure use Optional where it makes sense, probably most on APIs and >> SPIs, but please don't go overboard with it in internals. That's all I said >> in the original debate. >> > >> > In case you want to benchmark the impact of Optional make a JMH based >> microbenchmark - that's interesting to see what C2 is capable of - but even >> so that's not going to tell you much on the impact it would have to patch >> thousands of code all around Infinispan. And it will need some peer review >> before it can tell you anything at all ;) >> > >> > It's actually a very challenging topic, as we produce libraries meant >> for "anyone to use" and don't get to set the hardware specification >> requirements it's hard to predict if we should optimise the system for >> this/that resource consumption. Some people will have plenty of CPU and >> have problems with us needing too much memory, some others will have the >> opposite.. the real challenge is in making internals "elastic" to such >> factors and adaptable without making it too hard to tune. >> > >> > Thanks, >> > Sanne >> > >> > >> > >> > On 18 May 2017 at 12:30, Sebastian Laskawiec <slaskawi(a)redhat.com&gt; >> wrote: >> > Hey! >> > >> > In our past we had a couple of discussions about whether we should or >> should not use Optionals [1][2]. The main argument against it was >> performance. >> > >> > On one hand we risk additional object allocation (the Optional itself) >> and wrong inlining decisions taken by C2 compiler [3]. On the other hand we >> all probably "feel" that both of those things shouldn't be a problem and >> should be optimized by C2. Another argument was the Optional's doesn't give >> us anything but as I checked, we introduced nearly 80 NullPointerException >> bugs in two years [4]. So we might consider Optional as a way of fighting >> those things. The final argument that I've seen was about lack of higher >> order functions which is simply not true since we have #map, #filter and >> #flatmap functions. You can do pretty amazing things with this. >> > >> > I decided to check the performance when refactoring REST interface. I >> created a PR with Optionals [5], ran performance tests, removed all >> Optionals and reran tests. You will be surprised by the results [6]: >> > >> > Test case >> > With Optionals [%] Without Optionals >> > Run 1 Run 2 Avg Run 1 Run 2 Avg >> > Non-TX reads 10 threads >> > Throughput 32.54 32.87 32.71 31.74 34.04 32.89 >> > Response time -24.12 -24.63 -24.38 -24.37 -25.69 -25.03 >> > Non-TX reads 100 threads >> > Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 >> > Response time -6.15 14.93 4.39 7.88 6.49 7.19 >> > Non-TX writes 10 threads >> > Throughput 9.21 7.60 8.41 4.66 7.15 5.91 >> > Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 >> > Non-TX writes 100 threads >> > Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 >> > Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 >> > >> > I also created JMH + Flight Recorder tests and again, the results >> showed no evidence of slow down caused by Optionals [7]. >> > >> > Now please take those results with a grain of salt since they tend to >> drift by a factor of +/-5% (sometimes even more). But it's very clear the >> performance results are very similar if not the same. >> > >> > Having those numbers at hand, do we want to have Optionals in >> Infinispan codebase or not? And if not, let's state it very clearly (and >> write it into contributing guide), it's because we don't like them. Not >> because of performance. >> > >> > Thanks, >> > Sebastian >> > >> > [1] http://lists.jboss.org/pipermail/infinispan-dev/2017-March/ >> 017370.html >> > [2] http://lists.jboss.org/pipermail/infinispan-dev/2016-August/ >> 016796.html >> > [3] http://vanillajava.blogspot.ro/2015/01/java-lambdas-and-low- >> latency.html >> > [4] https://issues.jboss.org/issues/?jql=project%20%3D%20ISPN% >> 20AND%20issuetype%20%3D%20Bug%20AND%20text%20%7E%20% >> 22NullPointerException%22%20AND%20created%20%3E%3D%202015- >> 04-27%20AND%20created%20%3C%3D%202017-04-27 >> > [5] https://github.com/infinispan/infinispan/pull/5094 >> > [6] https://docs.google.com/a/redhat.com/spreadsheets/d/1oep6Was >> 0FfvHdqBCwpCFIqcPfJZ5-5_YYUqlRtUxEkM/edit?usp=sharing >> > [7] https://github.com/infinispan/infinispan/pull/5094#issuecomm >> ent-296970673 >> > -- >> > SEBASTIAN ŁASKAWIEC >> > INFINISPAN DEVELOPER >> > Red Hat EMEA >> > >> > >> > _______________________________________________ >> > infinispan-dev mailing list >> > infinispan-dev(a)lists.jboss.org >> > https://lists.jboss.org/mailman/listinfo/infinispan-dev >> > >> > _______________________________________________ >> > infinispan-dev mailing list >> > infinispan-dev(a)lists.jboss.org >> > https://lists.jboss.org/mailman/listinfo/infinispan-dev >> >> >> _______________________________________________ >> infinispan-dev mailing list >> infinispan-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/infinispan-dev > > -- > > SEBASTIAN ŁASKAWIEC > > INFINISPAN DEVELOPER > > Red Hat EMEA <https://www.redhat.com/> > <https://red.ht/sig> > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev > _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev

that you've become too ecstatic about Optionals. These should be used as return types for methods, not a) parameters to methods nor b) fields. This is a misuse of the API, according to the authors of Optionals in JDK. Most of the time, you're not using optionals to have fluent chain of method invocations, so -100 to that.

I haven't checked Sebastian's refactored code, but does it use Optionals as a *field* type? That's misuse (same as using it as an arg), it's intended solely as method return type. Radim On 05/23/2017 05:45 PM, Katia Aresti wrote: > Dan, I disagree with point 2 where you say "You now have a field that > could be null, Optional.empty(), or Optional.of(something)" > > This is the point of optional. You shouldn't have a field that has > these 3 possible values, just two of them = Some or None. If the field > is mutable, it should be initialised to Optional.empty(). In the case > of an API, Optional implicitly says that the return value can be > empty, but when you return a "normal" object, either the user reads > the doc, either will have bugs or boilerplate code defending from the > possible null value (even if never ever this API will return null) > > :o) > > Cheers > > > > On Tue, May 23, 2017 at 3:58 PM, Dan Berindei <dan.berindei(a)gmail.com > <mailto:dan.berindei@gmail.com>> wrote: > > I wouldn't say I'm an extreme naysayer, but I do have 2 issues > with Optional: > > 1. Performance becomes harder to quantify: the allocations may or > may not be eliminated, and a change in one part of the code may > change how allocations are eliminated in a completely different > part of the code. > 2. My personal opinion is it's just ugly... instead of having one > field that could be null or non-null, you now have a field that > could be null, Optional.empty(), or Optional.of(something). > > Cheers > Dan > > > > On Tue, May 23, 2017 at 1:54 PM, Sebastian Laskawiec > <slaskawi(a)redhat.com <mailto:slaskawi@redhat.com>> wrote: > > Hey! > > So I think we have no extreme naysayers to Optional. So let me > try to sum up what we have achieved so: > > * In macroscale benchmark based on REST interface using > Optionals didn't lower the performance. > * +1 for using it in public APIs, especially for those using > functional style. > * Creating lots of Optional instances might add some > pressure on GC, so we need to be careful when using them > in hot code paths. In such cases it is required to run a > micro scale benchamark to make sure the performance didn't > drop. The microbenchmark should also be followed by macro > scale benchamrk - PerfJobAck. Also, keep an eye on Eden > space in such cases. > > If you agree with me, and there are no hard evidence that > using Optional degrade performance significantly, I would like > to issue a pull request and put those findings into > contributing guide [1]. > > Thanks, > Sebastian > > [1] > https://github.com/infinispan/infinispan/tree/master/documentation/src/ma... > < https://github.com/infinispan/infinispan/tree/master/documentation/src/ma... > > > On Mon, May 22, 2017 at 6:36 PM Galder Zamarreño > <galder(a)redhat.com <mailto:galder@redhat.com>> wrote: > > I think Sanne's right here, any differences in such large > scale test are hard to decipher. > > Also, as mentioned in a previous email, my view on its > usage is same as Sanne's: > > * Definitely in APIs/SPIs. > * Be gentle with it internals. > > Cheers, > -- > Galder Zamarreño > Infinispan, Red Hat > > > On 18 May 2017, at 14:35, Sanne Grinovero > <sanne(a)infinispan.org <mailto:sanne@infinispan.org>> wrote: > > > > Hi Sebastian, > > > > sorry but I think you've been wasting time, I hope it > was fun :) This is not the right methodology to "settle" > the matter (unless you want Radim's eyes to get bloody..). > > > > Any change in such a complex system will only affect the > performance metrics if you're actually addressing the > dominant bottleneck. In some cases it might be CPU, like > if your system is at 90%+ CPU then it's likely that > reviewing the code to use less CPU would be beneficial; > but even that can be counter-productive, for example if > you're having contention caused by optimistic locking and > you fail to address that while making something else > "faster" the performance loss on the optimistic lock might > become asymptotic. > > > > A good reason to avoid excessive usage of Optional (and > *excessive* doesn't mean a couple dozen in a millions > lines of code..) is to not run out of eden space, > especially for all the code running in interpreted mode. > > > > In your case you've been benchmarking a hugely complex > beast, not least over REST! When running the REST Server I > doubt that allocation in eden is your main problem. You > just happened to have a couple Optionals on your path; > sure performance changed but there's no enough data in > this way to figure out what exactly happened: > > - did it change at all or was it just because of a > lucky optimisation? (The JIT will always optimise stuff > differently even when re-running the same code) > > - did the overall picture improve because this code > became much *less* slower? > > > > The real complexity in benchmarking is to accurately > understand why it changed; this should also tell you why > it didn't change more, or less.. > > > > To be fair I actually agree that it's very likely that > C2 can make any performance penalty disappear.. that's > totally possible, although it's unlikely to be faster than > just reading the field (assuming we don't need to do > branching because of null-checks but C2 can optimise that > as well). > > Still this requires the code to be optimised by JIT > first, so it won't prevent us from creating a gazillion of > instances if we abuse its usage irresponsibly. Fighting > internal NPEs is a matter of writing better code; I'm not > against some "Optional" being strategically placed but I > believe it's much nicer for most internal code to just > avoid null, use "final", and initialize things aggressively. > > > > Sure use Optional where it makes sense, probably most on > APIs and SPIs, but please don't go overboard with it in > internals. That's all I said in the original debate. > > > > In case you want to benchmark the impact of Optional > make a JMH based microbenchmark - that's interesting to > see what C2 is capable of - but even so that's not going > to tell you much on the impact it would have to patch > thousands of code all around Infinispan. And it will need > some peer review before it can tell you anything at all ;) > > > > It's actually a very challenging topic, as we produce > libraries meant for "anyone to use" and don't get to set > the hardware specification requirements it's hard to > predict if we should optimise the system for this/that > resource consumption. Some people will have plenty of CPU > and have problems with us needing too much memory, some > others will have the opposite.. the real challenge is in > making internals "elastic" to such factors and adaptable > without making it too hard to tune. > > > > Thanks, > > Sanne > > > > > > > > On 18 May 2017 at 12:30, Sebastian Laskawiec > <slaskawi(a)redhat.com <mailto:slaskawi@redhat.com>> wrote: > > Hey! > > > > In our past we had a couple of discussions about whether > we should or should not use Optionals [1][2]. The main > argument against it was performance. > > > > On one hand we risk additional object allocation (the > Optional itself) and wrong inlining decisions taken by C2 > compiler [3]. On the other hand we all probably "feel" > that both of those things shouldn't be a problem and > should be optimized by C2. Another argument was the > Optional's doesn't give us anything but as I checked, we > introduced nearly 80 NullPointerException bugs in two > years [4]. So we might consider Optional as a way of > fighting those things. The final argument that I've seen > was about lack of higher order functions which is simply > not true since we have #map, #filter and #flatmap > functions. You can do pretty amazing things with this. > > > > I decided to check the performance when refactoring REST > interface. I created a PR with Optionals [5], ran > performance tests, removed all Optionals and reran tests. > You will be surprised by the results [6]: > > > > Test case > > With Optionals [%] Without Optionals > > Run 1 Run 2 Avg Run 1 Run 2 Avg > > Non-TX reads 10 threads > > Throughput 32.54 32.87 32.71 31.74 34.04 32.89 > > Response time -24.12 -24.63 -24.38 -24.37 -25.69 -25.03 > > Non-TX reads 100 threads > > Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 > > Response time -6.15 14.93 4.39 7.88 6.49 7.19 > > Non-TX writes 10 threads > > Throughput 9.21 7.60 8.41 4.66 7.15 5.91 > > Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 > > Non-TX writes 100 threads > > Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 > > Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 > > > > I also created JMH + Flight Recorder tests and again, > the results showed no evidence of slow down caused by > Optionals [7]. > > > > Now please take those results with a grain of salt since > they tend to drift by a factor of +/-5% (sometimes even > more). But it's very clear the performance results are > very similar if not the same. > > > > Having those numbers at hand, do we want to have > Optionals in Infinispan codebase or not? And if not, let's > state it very clearly (and write it into contributing > guide), it's because we don't like them. Not because of > performance. > > > > Thanks, > > Sebastian > > > > [1] > http://lists.jboss.org/pipermail/infinispan-dev/2017-March/017370.html > < http://lists.jboss.org/pipermail/infinispan-dev/2017-March/017370.html> > > [2] > http://lists.jboss.org/pipermail/infinispan-dev/2016-August/016796.html > < http://lists.jboss.org/pipermail/infinispan-dev/2016-August/016796.html> > > [3] > http://vanillajava.blogspot.ro/2015/01/java-lambdas-and-low-latency.html > < http://vanillajava.blogspot.ro/2015/01/java-lambdas-and-low-latency.html> > > [4] > https://issues.jboss.org/issues/?jql=project%20%3D%20ISPN%20AND%20issuety... > < https://issues.jboss.org/issues/?jql=project%20%3D%20ISPN%20AND%20issuety... > > > [5] https://github.com/infinispan/infinispan/pull/5094 > <https://github.com/infinispan/infinispan/pull/5094> > > [6] > https://docs.google.com/a/redhat.com/spreadsheets/d/1oep6Was0FfvHdqBCwpCF... > < https://docs.google.com/a/redhat.com/spreadsheets/d/1oep6Was0FfvHdqBCwpCF... > > > [7] > https://github.com/infinispan/infinispan/pull/5094#issuecomment-296970673 > < https://github.com/infinispan/infinispan/pull/5094#issuecomment-296970673... > > -- > > SEBASTIAN ŁASKAWIEC > > INFINISPAN DEVELOPER > > Red Hat EMEA > > > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org > <mailto:infinispan-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org > <mailto:infinispan-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > <mailto:infinispan-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/infinispan-dev > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > -- > > SEBASTIANŁASKAWIEC > > INFINISPAN DEVELOPER > > Red HatEMEA <https://www.redhat.com/> > > <https://red.ht/sig> > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > <mailto:infinispan-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/infinispan-dev > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org <mailto: infinispan-dev(a)lists.jboss.org&gt; > https://lists.jboss.org/mailman/listinfo/infinispan-dev > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev -- Radim Vansa <rvansa(a)redhat.com&gt; JBoss Performance Team _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev

Adding part of your email from REST refactoring thread: Looking into the code, without considering performance at all, I think > that you've become too ecstatic about Optionals. These should be used as > return types for methods, not a) parameters to methods nor b) fields. > This is a misuse of the API, according to the authors of Optionals in > JDK. Most of the time, you're not using optionals to have fluent chain > of method invocations, so -100 to that. > I'm sorry I'm not picking up the discussion about REST refactoring PR since it has been already merged. Plus I'm not planning to do any Optionals refactoring as long I don't have a clear vision how we'd like to approach it. But I'm actually very happy you touched the use case topic. So far we were discussing advantages and disadvantages of Optionals and we didn't say much about potential use cases (Katia, Dan, Galder and Sanne also touched a little this topic). Indeed, Stephen Colebourne [1] mentions that it should be used as method return types: "My only fear is that Optional will be overused. Please focus on using it as a return type (from methods that perform some useful piece of functionality) Please don't use it as the field of a Java-Bean." Brian Goetz also said a few words on Stack Overflow about this [2]: "For example, you probably should never use it for something that returns an array of results, or a list of results; instead return an empty array or list. You should almost never use it as a field of something or a method parameter. I think routinely using it as a return value for getters would definitely be over-use." So if we want to be really dogmatic here, we wouldn't be able to use Optionals in fields, method parameters, and getters. Please note that I'm blindly putting recommendations mentioned above into code. As it turns out we can use Optionals anywhere, except method returning some objects which are not getters. It is also worth to say that both gentlemen are worried that Optionals might be overused in the libraries. On the other hand we have Oracle's tutorials which use Optionals as a fields [3]: "public class Soundcard { private Optional<USB> usb; public Optional<USB> getUSB() { ... } }" and say no word about recommendations mentioned in [1] and [2]. Also many libraries (like Jackson, Hibernate validator) support Optionals as fields [5]. So it must be somewhat popular use case right?

I think my favorit reading about Optional use cases is this [6]. So the author suggests to use Optionals as a return types in API boundaries but use nulls inside classes. This has two major advantages: - It makes the library caller aware that the value might not be there - The returned Optional object will probably die very soon (a called will probably do something with it right away) An example based on Oracle's tutorial would look like this (following this recommendation): "public class Soundcard { private USB usb; public Optional<USB> getUSB() { return Optional.ofNullable(usb); } }" I think it hits exactly into Katia's, Sanne's, Dan's and Galder's points. What do you think?

[1] http://blog.joda.org/2014/11/optional-in-java-se-8.html [2] https://stackoverflow.com/questions/26327957/should- java-8-getters-return-optional-type/26328555#26328555 [3] http://www.oracle.com/technetwork/articles/java/ java8-optional-2175753.html [4] http://blog.joda.org/2015/08/java-se-8-optional- pragmatic-approach.html [5] http://dolszewski.com/java/java-8-optional-use-cases/ [6] http://blog.joda.org/2015/08/java-se-8-optional- pragmatic-approach.html On Wed, May 24, 2017 at 4:56 PM Radim Vansa <rvansa(a)redhat.com&gt; wrote: > I haven't checked Sebastian's refactored code, but does it use Optionals > as a *field* type? That's misuse (same as using it as an arg), it's > intended solely as method return type. > > Radim > > On 05/23/2017 05:45 PM, Katia Aresti wrote: > > Dan, I disagree with point 2 where you say "You now have a field that > > could be null, Optional.empty(), or Optional.of(something)" > > > > This is the point of optional. You shouldn't have a field that has > > these 3 possible values, just two of them = Some or None. If the field > > is mutable, it should be initialised to Optional.empty(). In the case > > of an API, Optional implicitly says that the return value can be > > empty, but when you return a "normal" object, either the user reads > > the doc, either will have bugs or boilerplate code defending from the > > possible null value (even if never ever this API will return null) > > > > :o) > > > > Cheers > > > > > > > > On Tue, May 23, 2017 at 3:58 PM, Dan Berindei <dan.berindei(a)gmail.com > > <mailto:dan.berindei@gmail.com>> wrote: > > > > I wouldn't say I'm an extreme naysayer, but I do have 2 issues > > with Optional: > > > > 1. Performance becomes harder to quantify: the allocations may or > > may not be eliminated, and a change in one part of the code may > > change how allocations are eliminated in a completely different > > part of the code. > > 2. My personal opinion is it's just ugly... instead of having one > > field that could be null or non-null, you now have a field that > > could be null, Optional.empty(), or Optional.of(something). > > > > Cheers > > Dan > > > > > > > > On Tue, May 23, 2017 at 1:54 PM, Sebastian Laskawiec > > <slaskawi(a)redhat.com <mailto:slaskawi@redhat.com>> wrote: > > > > Hey! > > > > So I think we have no extreme naysayers to Optional. So let me > > try to sum up what we have achieved so: > > > > * In macroscale benchmark based on REST interface using > > Optionals didn't lower the performance. > > * +1 for using it in public APIs, especially for those using > > functional style. > > * Creating lots of Optional instances might add some > > pressure on GC, so we need to be careful when using them > > in hot code paths. In such cases it is required to run a > > micro scale benchamark to make sure the performance didn't > > drop. The microbenchmark should also be followed by macro > > scale benchamrk - PerfJobAck. Also, keep an eye on Eden > > space in such cases. > > > > If you agree with me, and there are no hard evidence that > > using Optional degrade performance significantly, I would like > > to issue a pull request and put those findings into > > contributing guide [1]. > > > > Thanks, > > Sebastian > > > > [1] > > https://github.com/infinispan/infinispan/tree/ > master/documentation/src/main/asciidoc/contributing > > <https://github.com/infinispan/infinispan/tree/ > master/documentation/src/main/asciidoc/contributing> > > > > On Mon, May 22, 2017 at 6:36 PM Galder Zamarreño > > <galder(a)redhat.com <mailto:galder@redhat.com>> wrote: > > > > I think Sanne's right here, any differences in such large > > scale test are hard to decipher. > > > > Also, as mentioned in a previous email, my view on its > > usage is same as Sanne's: > > > > * Definitely in APIs/SPIs. > > * Be gentle with it internals. > > > > Cheers, > > -- > > Galder Zamarreño > > Infinispan, Red Hat > > > > > On 18 May 2017, at 14:35, Sanne Grinovero > > <sanne(a)infinispan.org <mailto:sanne@infinispan.org>> wrote: > > > > > > Hi Sebastian, > > > > > > sorry but I think you've been wasting time, I hope it > > was fun :) This is not the right methodology to "settle" > > the matter (unless you want Radim's eyes to get bloody..). > > > > > > Any change in such a complex system will only affect the > > performance metrics if you're actually addressing the > > dominant bottleneck. In some cases it might be CPU, like > > if your system is at 90%+ CPU then it's likely that > > reviewing the code to use less CPU would be beneficial; > > but even that can be counter-productive, for example if > > you're having contention caused by optimistic locking and > > you fail to address that while making something else > > "faster" the performance loss on the optimistic lock might > > become asymptotic. > > > > > > A good reason to avoid excessive usage of Optional (and > > *excessive* doesn't mean a couple dozen in a millions > > lines of code..) is to not run out of eden space, > > especially for all the code running in interpreted mode. > > > > > > In your case you've been benchmarking a hugely complex > > beast, not least over REST! When running the REST Server I > > doubt that allocation in eden is your main problem. You > > just happened to have a couple Optionals on your path; > > sure performance changed but there's no enough data in > > this way to figure out what exactly happened: > > > - did it change at all or was it just because of a > > lucky optimisation? (The JIT will always optimise stuff > > differently even when re-running the same code) > > > - did the overall picture improve because this code > > became much *less* slower? > > > > > > The real complexity in benchmarking is to accurately > > understand why it changed; this should also tell you why > > it didn't change more, or less.. > > > > > > To be fair I actually agree that it's very likely that > > C2 can make any performance penalty disappear.. that's > > totally possible, although it's unlikely to be faster than > > just reading the field (assuming we don't need to do > > branching because of null-checks but C2 can optimise that > > as well). > > > Still this requires the code to be optimised by JIT > > first, so it won't prevent us from creating a gazillion of > > instances if we abuse its usage irresponsibly. Fighting > > internal NPEs is a matter of writing better code; I'm not > > against some "Optional" being strategically placed but I > > believe it's much nicer for most internal code to just > > avoid null, use "final", and initialize things aggressively. > > > > > > Sure use Optional where it makes sense, probably most on > > APIs and SPIs, but please don't go overboard with it in > > internals. That's all I said in the original debate. > > > > > > In case you want to benchmark the impact of Optional > > make a JMH based microbenchmark - that's interesting to > > see what C2 is capable of - but even so that's not going > > to tell you much on the impact it would have to patch > > thousands of code all around Infinispan. And it will need > > some peer review before it can tell you anything at all ;) > > > > > > It's actually a very challenging topic, as we produce > > libraries meant for "anyone to use" and don't get to set > > the hardware specification requirements it's hard to > > predict if we should optimise the system for this/that > > resource consumption. Some people will have plenty of CPU > > and have problems with us needing too much memory, some > > others will have the opposite.. the real challenge is in > > making internals "elastic" to such factors and adaptable > > without making it too hard to tune. > > > > > > Thanks, > > > Sanne > > > > > > > > > > > > On 18 May 2017 at 12:30, Sebastian Laskawiec > > <slaskawi(a)redhat.com <mailto:slaskawi@redhat.com>> wrote: > > > Hey! > > > > > > In our past we had a couple of discussions about whether > > we should or should not use Optionals [1][2]. The main > > argument against it was performance. > > > > > > On one hand we risk additional object allocation (the > > Optional itself) and wrong inlining decisions taken by C2 > > compiler [3]. On the other hand we all probably "feel" > > that both of those things shouldn't be a problem and > > should be optimized by C2. Another argument was the > > Optional's doesn't give us anything but as I checked, we > > introduced nearly 80 NullPointerException bugs in two > > years [4]. So we might consider Optional as a way of > > fighting those things. The final argument that I've seen > > was about lack of higher order functions which is simply > > not true since we have #map, #filter and #flatmap > > functions. You can do pretty amazing things with this. > > > > > > I decided to check the performance when refactoring REST > > interface. I created a PR with Optionals [5], ran > > performance tests, removed all Optionals and reran tests. > > You will be surprised by the results [6]: > > > > > > Test case > > > With Optionals [%] Without Optionals > > > Run 1 Run 2 Avg Run 1 Run 2 Avg > > > Non-TX reads 10 threads > > > Throughput 32.54 32.87 32.71 31.74 34.04 32.89 > > > Response time -24.12 -24.63 -24.38 -24.37 -25.69 > -25.03 > > > Non-TX reads 100 threads > > > Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 > > > Response time -6.15 14.93 4.39 7.88 6.49 7.19 > > > Non-TX writes 10 threads > > > Throughput 9.21 7.60 8.41 4.66 7.15 5.91 > > > Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 > > > Non-TX writes 100 threads > > > Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 > > > Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 > > > > > > I also created JMH + Flight Recorder tests and again, > > the results showed no evidence of slow down caused by > > Optionals [7]. > > > > > > Now please take those results with a grain of salt since > > they tend to drift by a factor of +/-5% (sometimes even > > more). But it's very clear the performance results are > > very similar if not the same. > > > > > > Having those numbers at hand, do we want to have > > Optionals in Infinispan codebase or not? And if not, let's > > state it very clearly (and write it into contributing > > guide), it's because we don't like them. Not because of > > performance. > > > > > > Thanks, > > > Sebastian > > > > > > [1] > > http://lists.jboss.org/pipermail/infinispan-dev/2017- > March/017370.html > > <http://lists.jboss.org/pipermail/infinispan-dev/2017- > March/017370.html> > > > [2] > > http://lists.jboss.org/pipermail/infinispan-dev/2016- > August/016796.html > > <http://lists.jboss.org/pipermail/infinispan-dev/2016- > August/016796.html> > > > [3] > > http://vanillajava.blogspot.ro/2015/01/java-lambdas-and- > low-latency.html > > <http://vanillajava.blogspot.ro/2015/01/java-lambdas-and- > low-latency.html> > > > [4] > > https://issues.jboss.org/issues/?jql=project%20%3D% > 20ISPN%20AND%20issuetype%20%3D%20Bug%20AND%20text%20%7E% > 20%22NullPointerException%22%20AND%20created%20%3E%3D% > 202015-04-27%20AND%20created%20%3C%3D%202017-04-27 > > <https://issues.jboss.org/issues/?jql=project%20%3D% > 20ISPN%20AND%20issuetype%20%3D%20Bug%20AND%20text%20%7E% > 20%22NullPointerException%22%20AND%20created%20%3E%3D% > 202015-04-27%20AND%20created%20%3C%3D%202017-04-27> > > > [5] https://github.com/infinispan/infinispan/pull/5094 > > <https://github.com/infinispan/infinispan/pull/5094> > > > [6] > > https://docs.google.com/a/redhat.com/spreadsheets/d/ > 1oep6Was0FfvHdqBCwpCFIqcPfJZ5-5_YYUqlRtUxEkM/edit?usp=sharing > > <https://docs.google.com/a/redhat.com/spreadsheets/d/ > 1oep6Was0FfvHdqBCwpCFIqcPfJZ5-5_YYUqlRtUxEkM/edit?usp=sharing> > > > [7] > > https://github.com/infinispan/infinispan/pull/ > 5094#issuecomment-296970673 > > <https://github.com/infinispan/infinispan/pull/ > 5094#issuecomment-296970673> > > > -- > > > SEBASTIAN ŁASKAWIEC > > > INFINISPAN DEVELOPER > > > Red Hat EMEA > > > > > > > > > _______________________________________________ > > > infinispan-dev mailing list > > > infinispan-dev(a)lists.jboss.org > > <mailto:infinispan-dev@lists.jboss.org> > > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > > > _______________________________________________ > > > infinispan-dev mailing list > > > infinispan-dev(a)lists.jboss.org > > <mailto:infinispan-dev@lists.jboss.org> > > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org > > <mailto:infinispan-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > -- > > > > SEBASTIANŁASKAWIEC > > > > INFINISPAN DEVELOPER > > > > Red HatEMEA <https://www.redhat.com/> > > > > <https://red.ht/sig> > > > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org > > <mailto:infinispan-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists. > jboss.org> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > <https://lists.jboss.org/mailman/listinfo/infinispan-dev> > > > > > > > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > > -- > Radim Vansa <rvansa(a)redhat.com&gt; > JBoss Performance Team > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/infinispan-dev -- SEBASTIAN ŁASKAWIEC INFINISPAN DEVELOPER Red Hat EMEA <https://www.redhat.com/> <https://red.ht/sig> _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev

Hey! So I think we have no extreme naysayers to Optional. So let me try to sum up what we have achieved so: * In macroscale benchmark based on REST interface using Optionals didn't lower the performance. * +1 for using it in public APIs, especially for those using functional style. * Creating lots of Optional instances might add some pressure on GC, so we need to be careful when using them in hot code paths. In such cases it is required to run a micro scale benchamark to make sure the performance didn't drop. The microbenchmark should also be followed by macro scale benchamrk - PerfJobAck. Also, keep an eye on Eden space in such cases. If you agree with me, and there are no hard evidence that using Optional degrade performance significantly, I would like to issue a pull request and put those findings into contributing guide [1]. Thanks, Sebastian [1] https://github.com/infinispan/infinispan/tree/master/documentation/src/ma... On Mon, May 22, 2017 at 6:36 PM Galder Zamarreño <galder(a)redhat.com <mailto:galder@redhat.com>> wrote: I think Sanne's right here, any differences in such large scale test are hard to decipher. Also, as mentioned in a previous email, my view on its usage is same as Sanne's: * Definitely in APIs/SPIs. * Be gentle with it internals. Cheers, -- Galder Zamarreño Infinispan, Red Hat > On 18 May 2017, at 14:35, Sanne Grinovero <sanne(a)infinispan.org <mailto:sanne@infinispan.org>> wrote: > > Hi Sebastian, > > sorry but I think you've been wasting time, I hope it was fun :) This is not the right methodology to "settle" the matter (unless you want Radim's eyes to get bloody..). > > Any change in such a complex system will only affect the performance metrics if you're actually addressing the dominant bottleneck. In some cases it might be CPU, like if your system is at 90%+ CPU then it's likely that reviewing the code to use less CPU would be beneficial; but even that can be counter-productive, for example if you're having contention caused by optimistic locking and you fail to address that while making something else "faster" the performance loss on the optimistic lock might become asymptotic. > > A good reason to avoid excessive usage of Optional (and *excessive* doesn't mean a couple dozen in a millions lines of code..) is to not run out of eden space, especially for all the code running in interpreted mode. > > In your case you've been benchmarking a hugely complex beast, not least over REST! When running the REST Server I doubt that allocation in eden is your main problem. You just happened to have a couple Optionals on your path; sure performance changed but there's no enough data in this way to figure out what exactly happened: > - did it change at all or was it just because of a lucky optimisation? (The JIT will always optimise stuff differently even when re-running the same code) > - did the overall picture improve because this code became much *less* slower? > > The real complexity in benchmarking is to accurately understand why it changed; this should also tell you why it didn't change more, or less.. > > To be fair I actually agree that it's very likely that C2 can make any performance penalty disappear.. that's totally possible, although it's unlikely to be faster than just reading the field (assuming we don't need to do branching because of null-checks but C2 can optimise that as well). > Still this requires the code to be optimised by JIT first, so it won't prevent us from creating a gazillion of instances if we abuse its usage irresponsibly. Fighting internal NPEs is a matter of writing better code; I'm not against some "Optional" being strategically placed but I believe it's much nicer for most internal code to just avoid null, use "final", and initialize things aggressively. > > Sure use Optional where it makes sense, probably most on APIs and SPIs, but please don't go overboard with it in internals. That's all I said in the original debate. > > In case you want to benchmark the impact of Optional make a JMH based microbenchmark - that's interesting to see what C2 is capable of - but even so that's not going to tell you much on the impact it would have to patch thousands of code all around Infinispan. And it will need some peer review before it can tell you anything at all ;) > > It's actually a very challenging topic, as we produce libraries meant for "anyone to use" and don't get to set the hardware specification requirements it's hard to predict if we should optimise the system for this/that resource consumption. Some people will have plenty of CPU and have problems with us needing too much memory, some others will have the opposite.. the real challenge is in making internals "elastic" to such factors and adaptable without making it too hard to tune. > > Thanks, > Sanne > > > > On 18 May 2017 at 12:30, Sebastian Laskawiec <slaskawi(a)redhat.com <mailto:slaskawi@redhat.com>> wrote: > Hey! > > In our past we had a couple of discussions about whether we should or should not use Optionals [1][2]. The main argument against it was performance. > > On one hand we risk additional object allocation (the Optional itself) and wrong inlining decisions taken by C2 compiler [3]. On the other hand we all probably "feel" that both of those things shouldn't be a problem and should be optimized by C2. Another argument was the Optional's doesn't give us anything but as I checked, we introduced nearly 80 NullPointerException bugs in two years [4]. So we might consider Optional as a way of fighting those things. The final argument that I've seen was about lack of higher order functions which is simply not true since we have #map, #filter and #flatmap functions. You can do pretty amazing things with this. > > I decided to check the performance when refactoring REST interface. I created a PR with Optionals [5], ran performance tests, removed all Optionals and reran tests. You will be surprised by the results [6]: > > Test case > With Optionals [%] Without Optionals > Run 1 Run 2 Avg Run 1 Run 2 Avg > Non-TX reads 10 threads > Throughput 32.54 32.87 32.71 31.74 34.04 32.89 > Response time -24.12 -24.63 -24.38 -24.37 -25.69 -25.03 > Non-TX reads 100 threads > Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 > Response time -6.15 14.93 4.39 7.88 6.49 7.19 > Non-TX writes 10 threads > Throughput 9.21 7.60 8.41 4.66 7.15 5.91 > Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 > Non-TX writes 100 threads > Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 > Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 > > I also created JMH + Flight Recorder tests and again, the results showed no evidence of slow down caused by Optionals [7]. > > Now please take those results with a grain of salt since they tend to drift by a factor of +/-5% (sometimes even more). But it's very clear the performance results are very similar if not the same. > > Having those numbers at hand, do we want to have Optionals in Infinispan codebase or not? And if not, let's state it very clearly (and write it into contributing guide), it's because we don't like them. Not because of performance. > > Thanks, > Sebastian > > [1] http://lists.jboss.org/pipermail/infinispan-dev/2017-March/017370.html > [2] http://lists.jboss.org/pipermail/infinispan-dev/2016-August/016796.html > [3] http://vanillajava.blogspot.ro/2015/01/java-lambdas-and-low-latency.html > [4] https://issues.jboss.org/issues/?jql=project%20%3D%20ISPN%20AND%20issuety... > [5] https://github.com/infinispan/infinispan/pull/5094 > [6] https://docs.google.com/a/redhat.com/spreadsheets/d/1oep6Was0FfvHdqBCwpCF... > [7] https://github.com/infinispan/infinispan/pull/5094#issuecomment-296970673 > -- > SEBASTIAN ŁASKAWIEC > INFINISPAN DEVELOPER > Red Hat EMEA > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/infinispan-dev _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/infinispan-dev -- SEBASTIANŁASKAWIEC INFINISPAN DEVELOPER Red HatEMEA <https://www.redhat.com/> <https://red.ht/sig> _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev

Indeed Bela, you're an extreme naysayer! :) I'm actually trying to get as many comments and arguments out of this discussion. I hope we will be able to iron out a general recommendation or approach how we want to treat Optionals. On Tue, May 23, 2017 at 10:14 PM Bela Ban <belaban(a)mailbox.org <mailto:belaban@mailbox.org>> wrote: Actually, I'm an extreme naysayer! I actually voiced concerns so I'm wondering where your assumption there are no naysayers is coming from... :-) On 23/05/17 1:54 PM, Sebastian Laskawiec wrote: > Hey! > > So I think we have no extreme naysayers to Optional. So let me try to > sum up what we have achieved so: > > * In macroscale benchmark based on REST interface using Optionals > didn't lower the performance. > * +1 for using it in public APIs, especially for those using > functional style. > * Creating lots of Optional instances might add some pressure on GC, > so we need to be careful when using them in hot code paths. In > such cases it is required to run a micro scale benchamark to make > sure the performance didn't drop. The microbenchmark should also > be followed by macro scale benchamrk - PerfJobAck. Also, keep an > eye on Eden space in such cases. > > If you agree with me, and there are no hard evidence that using > Optional degrade performance significantly, I would like to issue a > pull request and put those findings into contributing guide [1]. > > Thanks, > Sebastian > > [1] > https://github.com/infinispan/infinispan/tree/master/documentation/src/ma... > > On Mon, May 22, 2017 at 6:36 PM Galder Zamarreño <galder(a)redhat.com <mailto:galder@redhat.com> > <mailto:galder@redhat.com <mailto:galder@redhat.com>>> wrote: > > I think Sanne's right here, any differences in such large scale > test are hard to decipher. > > Also, as mentioned in a previous email, my view on its usage is > same as Sanne's: > > * Definitely in APIs/SPIs. > * Be gentle with it internals. > > Cheers, > -- > Galder Zamarreño > Infinispan, Red Hat > > > On 18 May 2017, at 14:35, Sanne Grinovero <sanne(a)infinispan.org <mailto:sanne@infinispan.org> > <mailto:sanne@infinispan.org <mailto:sanne@infinispan.org>>> wrote: > > > > Hi Sebastian, > > > > sorry but I think you've been wasting time, I hope it was fun :) > This is not the right methodology to "settle" the matter (unless > you want Radim's eyes to get bloody..). > > > > Any change in such a complex system will only affect the > performance metrics if you're actually addressing the dominant > bottleneck. In some cases it might be CPU, like if your system is > at 90%+ CPU then it's likely that reviewing the code to use less > CPU would be beneficial; but even that can be counter-productive, > for example if you're having contention caused by optimistic > locking and you fail to address that while making something else > "faster" the performance loss on the optimistic lock might become > asymptotic. > > > > A good reason to avoid excessive usage of Optional (and > *excessive* doesn't mean a couple dozen in a millions lines of > code..) is to not run out of eden space, especially for all the > code running in interpreted mode. > > > > In your case you've been benchmarking a hugely complex beast, > not least over REST! When running the REST Server I doubt that > allocation in eden is your main problem. You just happened to have > a couple Optionals on your path; sure performance changed but > there's no enough data in this way to figure out what exactly > happened: > > - did it change at all or was it just because of a lucky > optimisation? (The JIT will always optimise stuff differently even > when re-running the same code) > > - did the overall picture improve because this code became much > *less* slower? > > > > The real complexity in benchmarking is to accurately understand > why it changed; this should also tell you why it didn't change > more, or less.. > > > > To be fair I actually agree that it's very likely that C2 can > make any performance penalty disappear.. that's totally possible, > although it's unlikely to be faster than just reading the field > (assuming we don't need to do branching because of null-checks but > C2 can optimise that as well). > > Still this requires the code to be optimised by JIT first, so it > won't prevent us from creating a gazillion of instances if we > abuse its usage irresponsibly. Fighting internal NPEs is a matter > of writing better code; I'm not against some "Optional" being > strategically placed but I believe it's much nicer for most > internal code to just avoid null, use "final", and initialize > things aggressively. > > > > Sure use Optional where it makes sense, probably most on APIs > and SPIs, but please don't go overboard with it in internals. > That's all I said in the original debate. > > > > In case you want to benchmark the impact of Optional make a JMH > based microbenchmark - that's interesting to see what C2 is > capable of - but even so that's not going to tell you much on the > impact it would have to patch thousands of code all around > Infinispan. And it will need some peer review before it can tell > you anything at all ;) > > > > It's actually a very challenging topic, as we produce libraries > meant for "anyone to use" and don't get to set the hardware > specification requirements it's hard to predict if we should > optimise the system for this/that resource consumption. Some > people will have plenty of CPU and have problems with us needing > too much memory, some others will have the opposite.. the real > challenge is in making internals "elastic" to such factors and > adaptable without making it too hard to tune. > > > > Thanks, > > Sanne > > > > > > > > On 18 May 2017 at 12:30, Sebastian Laskawiec > <slaskawi(a)redhat.com <mailto:slaskawi@redhat.com> <mailto:slaskawi@redhat.com <mailto:slaskawi@redhat.com>>> wrote: > > Hey! > > > > In our past we had a couple of discussions about whether we > should or should not use Optionals [1][2]. The main argument > against it was performance. > > > > On one hand we risk additional object allocation (the Optional > itself) and wrong inlining decisions taken by C2 compiler [3]. On > the other hand we all probably "feel" that both of those things > shouldn't be a problem and should be optimized by C2. Another > argument was the Optional's doesn't give us anything but as I > checked, we introduced nearly 80 NullPointerException bugs in two > years [4]. So we might consider Optional as a way of fighting > those things. The final argument that I've seen was about lack of > higher order functions which is simply not true since we have > #map, #filter and #flatmap functions. You can do pretty amazing > things with this. > > > > I decided to check the performance when refactoring REST > interface. I created a PR with Optionals [5], ran performance > tests, removed all Optionals and reran tests. You will be > surprised by the results [6]: > > > > Test case > > With Optionals [%] Without Optionals > > Run 1 Run 2 Avg Run 1 Run 2 Avg > > Non-TX reads 10 threads > > Throughput 32.54 32.87 32.71 31.74 34.04 32.89 > > Response time -24.12 -24.63 -24.38 -24.37 -25.69 -25.03 > > Non-TX reads 100 threads > > Throughput 6.48 -12.79 -3.16 -7.06 -6.14 -6.60 > > Response time -6.15 14.93 4.39 7.88 6.49 7.19 > > Non-TX writes 10 threads > > Throughput 9.21 7.60 8.41 4.66 7.15 5.91 > > Response time -8.92 -7.11 -8.02 -5.29 -6.93 -6.11 > > Non-TX writes 100 threads > > Throughput 2.53 1.65 2.09 -1.16 4.67 1.76 > > Response time -2.13 -1.79 -1.96 0.91 -4.67 -1.88 > > > > I also created JMH + Flight Recorder tests and again, the > results showed no evidence of slow down caused by Optionals [7]. > > > > Now please take those results with a grain of salt since they > tend to drift by a factor of +/-5% (sometimes even more). But it's > very clear the performance results are very similar if not the same. > > > > Having those numbers at hand, do we want to have Optionals in > Infinispan codebase or not? And if not, let's state it very > clearly (and write it into contributing guide), it's because we > don't like them. Not because of performance. > > > > Thanks, > > Sebastian > > > > [1] > http://lists.jboss.org/pipermail/infinispan-dev/2017-March/017370.html > > [2] > http://lists.jboss.org/pipermail/infinispan-dev/2016-August/016796.html > > [3] > http://vanillajava.blogspot.ro/2015/01/java-lambdas-and-low-latency.html > > [4] > https://issues.jboss.org/issues/?jql=project%20%3D%20ISPN%20AND%20issuety... > > [5] https://github.com/infinispan/infinispan/pull/5094 > > [6] > https://docs.google.com/a/redhat.com/spreadsheets/d/1oep6Was0FfvHdqBCwpCF... > > [7] > https://github.com/infinispan/infinispan/pull/5094#issuecomment-296970673 > > -- > > SEBASTIAN ŁASKAWIEC > > INFINISPAN DEVELOPER > > Red Hat EMEA > > > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> > <mailto:infinispan-dev@lists.jboss.org <mailto:infinispan-dev@lists.jboss.org>> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > > > _______________________________________________ > > infinispan-dev mailing list > > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> > <mailto:infinispan-dev@lists.jboss.org <mailto:infinispan-dev@lists.jboss.org>> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> <mailto:infinispan-dev@lists.jboss.org <mailto:infinispan-dev@lists.jboss.org>> > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > -- > > SEBASTIANŁASKAWIEC > > INFINISPAN DEVELOPER > > Red HatEMEA <https://www.redhat.com/> > > <https://red.ht/sig> > > > > _______________________________________________ > infinispan-dev mailing list > infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/infinispan-dev -- Bela Ban, JGroups lead (http://www.jgroups.org) _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org <mailto:infinispan-dev@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/infinispan-dev -- SEBASTIANŁASKAWIEC INFINISPAN DEVELOPER Red HatEMEA <https://www.redhat.com/> <https://red.ht/sig> _______________________________________________ infinispan-dev mailing list infinispan-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev