When JIRA was being screwy on Friday I used the time to investigate an idea I have had for a while about improving our boot time performance. According to Yourkit the majority of our time is spent in class loading. It seems very unlikely that we will be able to reduce the number of classes we load on boot (or at the very least it would be a massive amount of work) so I investigated a different approach. I modified ModuleClassLoader to spit out the name and module of every class that is loaded at boot time, and stored this in a properties file. I then created a simple Service that starts immediately that uses two threads to eagerly load every class on this list (I used two threads because that seemed to work well on my laptop, I think Runtime.availableProcessors()/4 is probably the best amount, but that assumption would need to be tested on different hardware). The idea behind this is that we know the classes will be used at some point, and we generally do not fully utilise all CPU's during boot, so we can use the unused CPU to pre load these classes so they are ready when they are actually required. Using this approach I saw the boot time for standalone.xml drop from ~2.9s to ~2.3s on my laptop. The (super hacky) code I used to perform this test is at https://github.com/wildfly/wildfly-core/compare/master... stuartwdouglas:boot-performance-hack I think these initial results are encouraging, and it is a big enough gain that I think it is worth investigating further. Firstly it would be great if I could get others to try it out and see if they see similar gains to boot time, it may be that the gain is very system dependent. Secondly if we do decide to do this there are two approach that we can use that I can see: 1) A hard coded list of class names that we generate before a release (basically what the hack already does), this is simplest, but does add a little bit of additional work to the release process (although if it is missed it would be no big deal, as ClassNotFoundException's would be suppressed, and if a few classes are missing the performance impact is negligible as long as the majority of the list is correct). 2) Generate the list dynamically on first boot, and store it in the temp directory. This would require the addition of a hook into JBoss Modules to generate the list, but is the approach I would prefer (as first boot is always a bit slower anyway). Thoughts? Stuart _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

On May 15, 2017, at 7:27 AM, Rostislav Svoboda <rsvoboda(a)redhat.com&gt; wrote: Hi. I can confirm I see improvements in boot time with your changes. My HW is Lenovo T440s with Fedora 25, Intel(R) Core(TM) i7-4600U CPU (Base Frequency 2.10 GHz, Max Turbo 3.30 GHz) I executed 50 iterations of start - stop sequence [1], before execution 5x start - stop for "warmup" With your changes Min: 3116 Max: 3761 Average: 3247.640000 Without: Min: 3442 Max: 4081 Average: 3580.840000 > 1) A hard coded list of class names that we generate before a release This will improve first boot impression, little bit harder for maintaining the list for the final build. Property files could be located inside properties directory of dedicated module (<resource-root path="properties"/>). Properties directory could contain property files for delivered profiles. Layered products or customer modifications could deliver own property file. e.g. predefined property file for standalone-openshift.xml in EAP image in OpenShift environment, I think they boot the server just once and throw away the whole docker image when something changes. > 2) Generate the list dynamically on first boot, and store it in the temp This looks like the most elegant thing to do. Question is how it will slow down the initial boot. People care about first boot impression, some blog writers do the mistake too. This would also block boot time improvements for use-cases when you start the server just once - e.g. Docker, OpenShift. Also the logic should take into account which profile is loaded - e.g standalone.xml vs. standalone-full-ha.xml Rostislav [1] rm wildfly-11.0.0.Beta1-SNAPSHOT-preload/standalone/log/server.log rm wildfly-11.0.0.Beta1-SNAPSHOT/standalone/log/server.log for i in {1..50}; do echo $i wildfly-11.0.0.Beta1-SNAPSHOT-preload/bin/standalone.sh 1>/dev/null 2>&1 & sleep 8 wildfly-11.0.0.Beta1-SNAPSHOT-preload/bin/jboss-cli.sh -c :shutdown 1>/dev/null 2>&1 done grep WFLYSRV0025 wildfly-11.0.0.Beta1-SNAPSHOT-preload/standalone/log/server.log | sed "s/.*\(....\)ms.*/\1/g" | awk 'NR == 1 { max=$1; min=$1; sum=0 } { if ($1>max) max=$1; if ($1<min) min=$1; sum+=$1;} END {printf "Min: %d\tMax: %d\tAverage: %f\n", min, max, sum/NR}' for i in {1..50}; do echo $i wildfly-11.0.0.Beta1-SNAPSHOT/bin/standalone.sh 1>/dev/null 2>&1 & sleep 8 wildfly-11.0.0.Beta1-SNAPSHOT/bin/jboss-cli.sh -c :shutdown 1>/dev/null 2>&1 done grep WFLYSRV0025 wildfly-11.0.0.Beta1-SNAPSHOT/standalone/log/server.log | sed "s/.*\(....\)ms.*/\1/g" | awk 'NR == 1 { max=$1; min=$1; sum=0 } { if ($1>max) max=$1; if ($1<min) min=$1; sum+=$1;} END {printf "Min: %d\tMax: %d\tAverage: %f\n", min, max, sum/NR}' ----- Original Message ----- > When JIRA was being screwy on Friday I used the time to investigate an idea I > have had for a while about improving our boot time performance. According to > Yourkit the majority of our time is spent in class loading. It seems very > unlikely that we will be able to reduce the number of classes we load on > boot (or at the very least it would be a massive amount of work) so I > investigated a different approach. > > I modified ModuleClassLoader to spit out the name and module of every class > that is loaded at boot time, and stored this in a properties file. I then > created a simple Service that starts immediately that uses two threads to > eagerly load every class on this list (I used two threads because that > seemed to work well on my laptop, I think Runtime.availableProcessors()/4 is > probably the best amount, but that assumption would need to be tested on > different hardware). > > The idea behind this is that we know the classes will be used at some point, > and we generally do not fully utilise all CPU's during boot, so we can use > the unused CPU to pre load these classes so they are ready when they are > actually required. > > Using this approach I saw the boot time for standalone.xml drop from ~2.9s to > ~2.3s on my laptop. The (super hacky) code I used to perform this test is at > https://github.com/wildfly/wildfly-core/compare/master...stuartwdouglas:b... > > I think these initial results are encouraging, and it is a big enough gain > that I think it is worth investigating further. > > Firstly it would be great if I could get others to try it out and see if they > see similar gains to boot time, it may be that the gain is very system > dependent. > > Secondly if we do decide to do this there are two approach that we can use > that I can see: > > 1) A hard coded list of class names that we generate before a release > (basically what the hack already does), this is simplest, but does add a > little bit of additional work to the release process (although if it is > missed it would be no big deal, as ClassNotFoundException's would be > suppressed, and if a few classes are missing the performance impact is > negligible as long as the majority of the list is correct). > > 2) Generate the list dynamically on first boot, and store it in the temp > directory. This would require the addition of a hook into JBoss Modules to > generate the list, but is the approach I would prefer (as first boot is > always a bit slower anyway). > > Thoughts? > > Stuart > > _______________________________________________ > wildfly-dev mailing list > wildfly-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/wildfly-dev _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

On May 15, 2017, at 9:23 AM, Sanne Grinovero <sanne(a)hibernate.org&gt; wrote: Very interesting. > From a different perspective, but closely related, I was recently trying to profile the testsuites of Hibernate projects and also in our case ClassLoader time is significant portion of the bootstrap time. In the Hibernate case I noticed it spends quite some time to locate Service implementations over the ServiceLoader pattern. The problem seems to be that a lot of internal code has been refactored in recent versions to be "replaceable" so Hibernate ORM includes a default implementation for each internal Service but it will first check if it can find an alternative somewhere else on the classpath: looking both among its own dependencies and among the classes provided by the deployment. I'll see if we can do better in Hibernate ORM (not sure yet!), but raising it here as I suspect several other libraries could be guilty of the same approach. I also hope we'll be able to curate (trim) the dependencies more; the current JPA subsystem is including many dependencies of questionable usefulness. That should help? Thanks, Sanne On 15 May 2017 at 13:27, Rostislav Svoboda <rsvoboda(a)redhat.com&gt; wrote: > Hi. > > I can confirm I see improvements in boot time with your changes. > My HW is Lenovo T440s with Fedora 25, Intel(R) Core(TM) i7-4600U CPU (Base Frequency 2.10 GHz, Max Turbo 3.30 GHz) > > I executed 50 iterations of start - stop sequence [1], before execution 5x start - stop for "warmup" > > With your changes > Min: 3116 Max: 3761 Average: 3247.640000 > > Without: > Min: 3442 Max: 4081 Average: 3580.840000 > > >> 1) A hard coded list of class names that we generate before a release > > This will improve first boot impression, little bit harder for maintaining the list for the final build. > > Property files could be located inside properties directory of dedicated module (<resource-root path="properties"/>). Properties directory could contain property files for delivered profiles. > > Layered products or customer modifications could deliver own property file. > e.g. predefined property file for standalone-openshift.xml in EAP image in OpenShift environment, I think they boot the server just once and throw away the whole docker image when something changes. > > >> 2) Generate the list dynamically on first boot, and store it in the temp > > This looks like the most elegant thing to do. Question is how it will slow down the initial boot. People care about first boot impression, some blog writers do the mistake too. > This would also block boot time improvements for use-cases when you start the server just once - e.g. Docker, OpenShift. > > Also the logic should take into account which profile is loaded - e.g standalone.xml vs. standalone-full-ha.xml > > Rostislav > > [1] > rm wildfly-11.0.0.Beta1-SNAPSHOT-preload/standalone/log/server.log > rm wildfly-11.0.0.Beta1-SNAPSHOT/standalone/log/server.log > > for i in {1..50}; do > echo $i > wildfly-11.0.0.Beta1-SNAPSHOT-preload/bin/standalone.sh 1>/dev/null 2>&1 & > sleep 8 > wildfly-11.0.0.Beta1-SNAPSHOT-preload/bin/jboss-cli.sh -c :shutdown 1>/dev/null 2>&1 > done > grep WFLYSRV0025 wildfly-11.0.0.Beta1-SNAPSHOT-preload/standalone/log/server.log | sed "s/.*\(....\)ms.*/\1/g" | awk 'NR == 1 { max=$1; min=$1; sum=0 } > { if ($1>max) max=$1; if ($1<min) min=$1; sum+=$1;} > END {printf "Min: %d\tMax: %d\tAverage: %f\n", min, max, sum/NR}' > > > for i in {1..50}; do > echo $i > wildfly-11.0.0.Beta1-SNAPSHOT/bin/standalone.sh 1>/dev/null 2>&1 & > sleep 8 > wildfly-11.0.0.Beta1-SNAPSHOT/bin/jboss-cli.sh -c :shutdown 1>/dev/null 2>&1 > done > grep WFLYSRV0025 wildfly-11.0.0.Beta1-SNAPSHOT/standalone/log/server.log | sed "s/.*\(....\)ms.*/\1/g" | awk 'NR == 1 { max=$1; min=$1; sum=0 } > { if ($1>max) max=$1; if ($1<min) min=$1; sum+=$1;} > END {printf "Min: %d\tMax: %d\tAverage: %f\n", min, max, sum/NR}' > > > ----- Original Message ----- >> When JIRA was being screwy on Friday I used the time to investigate an idea I >> have had for a while about improving our boot time performance. According to >> Yourkit the majority of our time is spent in class loading. It seems very >> unlikely that we will be able to reduce the number of classes we load on >> boot (or at the very least it would be a massive amount of work) so I >> investigated a different approach. >> >> I modified ModuleClassLoader to spit out the name and module of every class >> that is loaded at boot time, and stored this in a properties file. I then >> created a simple Service that starts immediately that uses two threads to >> eagerly load every class on this list (I used two threads because that >> seemed to work well on my laptop, I think Runtime.availableProcessors()/4 is >> probably the best amount, but that assumption would need to be tested on >> different hardware). >> >> The idea behind this is that we know the classes will be used at some point, >> and we generally do not fully utilise all CPU's during boot, so we can use >> the unused CPU to pre load these classes so they are ready when they are >> actually required. >> >> Using this approach I saw the boot time for standalone.xml drop from ~2.9s to >> ~2.3s on my laptop. The (super hacky) code I used to perform this test is at >> https://github.com/wildfly/wildfly-core/compare/master...stuartwdouglas:b... >> >> I think these initial results are encouraging, and it is a big enough gain >> that I think it is worth investigating further. >> >> Firstly it would be great if I could get others to try it out and see if they >> see similar gains to boot time, it may be that the gain is very system >> dependent. >> >> Secondly if we do decide to do this there are two approach that we can use >> that I can see: >> >> 1) A hard coded list of class names that we generate before a release >> (basically what the hack already does), this is simplest, but does add a >> little bit of additional work to the release process (although if it is >> missed it would be no big deal, as ClassNotFoundException's would be >> suppressed, and if a few classes are missing the performance impact is >> negligible as long as the majority of the list is correct). >> >> 2) Generate the list dynamically on first boot, and store it in the temp >> directory. This would require the addition of a hook into JBoss Modules to >> generate the list, but is the approach I would prefer (as first boot is >> always a bit slower anyway). >> >> Thoughts? >> >> Stuart >> >> _______________________________________________ >> wildfly-dev mailing list >> wildfly-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/wildfly-dev > _______________________________________________ > wildfly-dev mailing list > wildfly-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/wildfly-dev _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

>> 2) Generate the list dynamically on first boot, and store it in the temp > > This looks like the most elegant thing to do. Question is how it will slow > down the initial boot. People care about first boot impression, some blog > writers do the mistake too. > It will not actually slow down the initial boot (at least not in a measurable way), but the first boot would not get the benefit of this optimisation.

On May 14, 2017, at 6:36 PM, Stuart Douglas <stuart.w.douglas(a)gmail.com&gt; wrote: When JIRA was being screwy on Friday I used the time to investigate an idea I have had for a while about improving our boot time performance. According to Yourkit the majority of our time is spent in class loading. It seems very unlikely that we will be able to reduce the number of classes we load on boot (or at the very least it would be a massive amount of work) so I investigated a different approach. I modified ModuleClassLoader to spit out the name and module of every class that is loaded at boot time, and stored this in a properties file. I then created a simple Service that starts immediately that uses two threads to eagerly load every class on this list (I used two threads because that seemed to work well on my laptop, I think Runtime.availableProcessors()/4 is probably the best amount, but that assumption would need to be tested on different hardware). The idea behind this is that we know the classes will be used at some point, and we generally do not fully utilise all CPU's during boot, so we can use the unused CPU to pre load these classes so they are ready when they are actually required. Using this approach I saw the boot time for standalone.xml drop from ~2.9s to ~2.3s on my laptop. The (super hacky) code I used to perform this test is at https://github.com/wildfly/wildfly-core/compare/master...stuartwdouglas:b... I think these initial results are encouraging, and it is a big enough gain that I think it is worth investigating further. Firstly it would be great if I could get others to try it out and see if they see similar gains to boot time, it may be that the gain is very system dependent. Secondly if we do decide to do this there are two approach that we can use that I can see: 1) A hard coded list of class names that we generate before a release (basically what the hack already does), this is simplest, but does add a little bit of additional work to the release process (although if it is missed it would be no big deal, as ClassNotFoundException's would be suppressed, and if a few classes are missing the performance impact is negligible as long as the majority of the list is correct). 2) Generate the list dynamically on first boot, and store it in the temp directory. This would require the addition of a hook into JBoss Modules to generate the list, but is the approach I would prefer (as first boot is always a bit slower anyway). Thoughts? Stuart _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

On May 15, 2017, at 10:04 AM, Tomaž Cerar <tomaz.cerar(a)gmail.com&gt; wrote: On Mon, May 15, 2017 at 4:13 PM, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: So why does adding two more make such a big difference? Main reason is that this two threads load most of later required classes which can later be quickly loaded from multiple parallel threads. Currently concurrency causes that 8 -16 threads (on 4-8 logical core systems) try to load same classes at same time. this leads to lots of contention as result. "preloading" some of this classes reduces contention. Looking at the list in the current "hack impl" there are lots of classes that don't need to be there, stuff like subsystem parsers which are only loaded once in any case. Main pressure is on classes from jboss-modules, controller, server & xml parsers modules, all others are not as problematic. This is also reason why lots of contention is happening on JDK classes as well as those are shared between all parts of server code.

On May 17, 2017, at 1:42 PM, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: > On May 15, 2017, at 10:04 AM, Tomaž Cerar <tomaz.cerar(a)gmail.com&gt; wrote: > > > On Mon, May 15, 2017 at 4:13 PM, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: > So why does adding two more make such a big difference? > > Main reason is that this two threads load most of later required classes which can later be quickly loaded from multiple parallel threads. > > Currently concurrency causes that 8 -16 threads (on 4-8 logical core systems) try to load same classes at same time. > this leads to lots of contention as result. "preloading" some of this classes reduces contention. > > Looking at the list in the current "hack impl" there are lots of classes that don't need to be there, stuff like subsystem parsers which are only loaded once in any case. > > Main pressure is on classes from jboss-modules, controller, server & xml parsers modules, all others are not as problematic. > This is also reason why lots of contention is happening on JDK classes as well as those are shared between all parts of server code. > Stuart/Tomaz — Please ignore this for now if your thinking has moved on to other approaches, e.g. better concurrency in classloading. :) Otherwise, are there any numbers on this last point Tomaz made? I ask because people are asking for a static list since a dynamic list is of no benefit to cloud use cases. A static list is painful to administer though, and if not administered well can result in loading unneeded classes and wasting memory. But, a static list limited to modules that are part of the WildFly Core kernel is not particularly hard to administer. So if we can get the bulk of the gains with the minimum of the pain, we might consider that.

On 17 May 2017, at 22:45, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: > On May 17, 2017, at 3:29 PM, Jason Greene <jason.greene(a)redhat.com&gt; wrote: > > >> On May 17, 2017, at 1:42 PM, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: >> >> >>> On May 15, 2017, at 10:04 AM, Tomaž Cerar <tomaz.cerar(a)gmail.com&gt; wrote: >>> >>> >>> On Mon, May 15, 2017 at 4:13 PM, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: >>> So why does adding two more make such a big difference? >>> >>> Main reason is that this two threads load most of later required classes which can later be quickly loaded from multiple parallel threads. >>> >>> Currently concurrency causes that 8 -16 threads (on 4-8 logical core systems) try to load same classes at same time. >>> this leads to lots of contention as result. "preloading" some of this classes reduces contention. >>> >>> Looking at the list in the current "hack impl" there are lots of classes that don't need to be there, stuff like subsystem parsers which are only loaded once in any case. >>> >>> Main pressure is on classes from jboss-modules, controller, server & xml parsers modules, all others are not as problematic. >>> This is also reason why lots of contention is happening on JDK classes as well as those are shared between all parts of server code. >>> >> >> Stuart/Tomaz — >> >> Please ignore this for now if your thinking has moved on to other approaches, e.g. better concurrency in classloading. :) >> >> Otherwise, are there any numbers on this last point Tomaz made? >> >> I ask because people are asking for a static list since a dynamic list is of no benefit to cloud use cases. >> >> A static list is painful to administer though, and if not administered well can result in loading unneeded classes and wasting memory. >> >> But, a static list limited to modules that are part of the WildFly Core kernel is not particularly hard to administer. So if we can get the bulk of the gains with the minimum of the pain, we might consider that. >> > > We can also just have a dynamic offline list generation, which is ran as a build task. Yes, that’s my assumption. When I say “static” I mean static on a given installation. If it is limited to the kernel (including relevant JDK bits), then there are no issues with ensuring different feature pack maintainers are doing this, no need to combine lists from different parts of the build, no worries about ensuring only those bits relevant to what the user is actually running are loaded, etc. Those things are the “painful to administer part”. They might very well be worth it but data should demonstrate that.

-- Brian Stansberry Manager, Senior Principal Software Engineer JBoss by Red Hat _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

On Thu, May 18, 2017 at 10:28 AM, Kabir Khan <kabir.khan(a)jboss.com&gt; wrote: > > > If it is limited to the kernel (including relevant JDK bits), then there > > are no issues with ensuring different feature pack maintainers are doing > > this, no need to combine lists from different parts of the build, no worries > > about ensuring only those bits relevant to what the user is actually running > > are loaded, etc. Those things are the “painful to administer part”. They > > might very well be worth it but data should demonstrate that. > If it turns out to be worth it, the feature pack generation stuff could be > enhanced to generate the list for each config. Perhaps only if doing > -Prelease so we don't slow down everybody's builds while developing I think that only core stuff should need this, as there is where most of contention for class loading is. As all extension need classes from core it is most contested. So I think if we go with this, jdk + core would be the yield best work / benefit results

From the time I did parallel boot I’ve always wondered if the level of concurrency was valid, but I never got around to doing any experimentation.

On May 15, 2017, at 4:52 PM, Stuart Douglas <stuart.w.douglas(a)gmail.com&gt; wrote: On Tue, May 16, 2017 at 12:13 AM, Brian Stansberry <brian.stansberry(a)redhat.com&gt; wrote: Definitely worth investigating. I’d like to have a real good understanding of why it has the benefits it has, so we can see if this is the best way to get them or if something else is better. I am pretty sure it is contention related. I modified my hack to load all classes from the same module at once (so once the first class from a module in that properties file is reached, it loads all others from the same module), and this gave another small but significant speedup (so the total gain is ~2.0-2.1s down from ~2.9s). Looking at the results of monitor profiling in Yourkit it looks like the reason is reduced contention. There is 50% less thread wait time on ModuleLoader$FutureModule, contention on JarFileResourceLoader is no more. I think the reason is that we have a lot of threads active at boot and this results in a lot of contention in module/class loading. Stuart This kicks in just before the ModelController starts and begins parsing the config. The config parsing quickly gets into parallel work; as soon as the extension elements are reached the extension modules are loaded concurrently. Then once the parsing is done each subsystem is installed concurrently, so lots of threads doing concurrent classloading. So why does adding two more make such a big difference? Is it that they gets lots of work done in that time when the regular boot thread is not doing concurrent work, i.e. the parsing and the non-parallel bits of operation execution? Is it that these threads are just chugging along doing classloading efficiently while the parallel threads are running along inefficiently getting scheduled and unscheduled? The latter doesn’t make sense to me as there’s no reason why these threads would be any more efficient than the others. - Brian > On May 14, 2017, at 6:36 PM, Stuart Douglas <stuart.w.douglas(a)gmail.com&gt; wrote: > > When JIRA was being screwy on Friday I used the time to investigate an idea I have had for a while about improving our boot time performance. According to Yourkit the majority of our time is spent in class loading. It seems very unlikely that we will be able to reduce the number of classes we load on boot (or at the very least it would be a massive amount of work) so I investigated a different approach. > > I modified ModuleClassLoader to spit out the name and module of every class that is loaded at boot time, and stored this in a properties file. I then created a simple Service that starts immediately that uses two threads to eagerly load every class on this list (I used two threads because that seemed to work well on my laptop, I think Runtime.availableProcessors()/4 is probably the best amount, but that assumption would need to be tested on different hardware). > > The idea behind this is that we know the classes will be used at some point, and we generally do not fully utilise all CPU's during boot, so we can use the unused CPU to pre load these classes so they are ready when they are actually required. > > Using this approach I saw the boot time for standalone.xml drop from ~2.9s to ~2.3s on my laptop. The (super hacky) code I used to perform this test is at https://github.com/wildfly/wildfly-core/compare/master...stuartwdouglas:b... > > I think these initial results are encouraging, and it is a big enough gain that I think it is worth investigating further. > > Firstly it would be great if I could get others to try it out and see if they see similar gains to boot time, it may be that the gain is very system dependent. > > Secondly if we do decide to do this there are two approach that we can use that I can see: > > 1) A hard coded list of class names that we generate before a release (basically what the hack already does), this is simplest, but does add a little bit of additional work to the release process (although if it is missed it would be no big deal, as ClassNotFoundException's would be suppressed, and if a few classes are missing the performance impact is negligible as long as the majority of the list is correct). > > 2) Generate the list dynamically on first boot, and store it in the temp directory. This would require the addition of a hook into JBoss Modules to generate the list, but is the approach I would prefer (as first boot is always a bit slower anyway). > > Thoughts? > > Stuart > _______________________________________________ > wildfly-dev mailing list > wildfly-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/wildfly-dev -- Brian Stansberry Manager, Senior Principal Software Engineer JBoss by Red Hat

I have a few thoughts that might be of interest. Firstly, I'd be interested to see when you are logging the class name being loaded. If you are logging it in loadClass, you might not be seeing the actual correct load order because that method is ultimately recursive. To get an accurate picture of what order that classes are actually defined - and thus what order you can load them in order to prevent contention on per-class locks within the CL - you should log immediately _after_ defineClass completes for each class.

Secondly, while debugging a resource iteration performance problem a user was having with a large number of deployments, I discovered that contention for the lock on JarFile and ZipFile was a primary cause. The workaround I employed was to keep a RAM-based List of the files in the JAR, which can be iterated over without touching the lock. When we're preloading classes, we're definitely going to see this same kind of contention come up, because there's only one lock per JarFile instance so you can only ever read one entry at a time, thus preventing any kind of useful concurrency on a per-module basis.

Exploding the files out of the JarFile could expose this contention and therefore might be useful as a test - but it would also skew the results a little because you have no decompression overhead, and creating the separate file streams hypothetically might be somewhat more (or less) expensive. I joked about resurrecting jzipfile (which I killed off because it was something like 20% slower at decompressing entries than Jar/ZipFile) but it might be worth considering having our own JAR extractor at some point with a view towards concurrency gains. If we go this route, we could go even further and create an optimized module format, which is an idea I think we've looked at a little bit in the past; there are a few avenues of exploration here which could be interesting.

At some point we also need to see how jaotc might improve things. It probably won't improve class loading time directly, but it might improve the processes by which class loading is done because all the one-off bits would be precompiled. Also it's worth exploring whether the jimage format has contention issues like this. On 05/14/2017 06:36 PM, Stuart Douglas wrote: > When JIRA was being screwy on Friday I used the time to investigate an > idea I have had for a while about improving our boot time performance. > According to Yourkit the majority of our time is spent in class loading. > It seems very unlikely that we will be able to reduce the number of > classes we load on boot (or at the very least it would be a massive > amount of work) so I investigated a different approach. > > I modified ModuleClassLoader to spit out the name and module of every > class that is loaded at boot time, and stored this in a properties file. > I then created a simple Service that starts immediately that uses two > threads to eagerly load every class on this list (I used two threads > because that seemed to work well on my laptop, I think > Runtime.availableProcessors()/4 is probably the best amount, but that > assumption would need to be tested on different hardware). > > The idea behind this is that we know the classes will be used at some > point, and we generally do not fully utilise all CPU's during boot, so > we can use the unused CPU to pre load these classes so they are ready > when they are actually required. > > Using this approach I saw the boot time for standalone.xml drop from > ~2.9s to ~2.3s on my laptop. The (super hacky) code I used to perform > this test is at > https://github.com/wildfly/wildfly-core/compare/master... stuartwdouglas:boot-performance-hack > > I think these initial results are encouraging, and it is a big enough > gain that I think it is worth investigating further. > > Firstly it would be great if I could get others to try it out and see if > they see similar gains to boot time, it may be that the gain is very > system dependent. > > Secondly if we do decide to do this there are two approach that we can > use that I can see: > > 1) A hard coded list of class names that we generate before a release > (basically what the hack already does), this is simplest, but does add a > little bit of additional work to the release process (although if it is > missed it would be no big deal, as ClassNotFoundException's would be > suppressed, and if a few classes are missing the performance impact is > negligible as long as the majority of the list is correct). > > 2) Generate the list dynamically on first boot, and store it in the temp > directory. This would require the addition of a hook into JBoss Modules > to generate the list, but is the approach I would prefer (as first boot > is always a bit slower anyway). > > Thoughts? > > Stuart > > > _______________________________________________ > wildfly-dev mailing list > wildfly-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/wildfly-dev > -- - DML _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

On 05/15/2017 05:21 PM, Stuart Douglas wrote: > On Tue, May 16, 2017 at 1:34 AM, David M. Lloyd <david.lloyd(a)redhat.com&gt; wrote: >> Exploding the files out of the JarFile could expose this contention and >> therefore might be useful as a test - but it would also skew the results >> a little because you have no decompression overhead, and creating the >> separate file streams hypothetically might be somewhat more (or less) >> expensive. I joked about resurrecting jzipfile (which I killed off >> because it was something like 20% slower at decompressing entries than >> Jar/ZipFile) but it might be worth considering having our own JAR >> extractor at some point with a view towards concurrency gains. If we go >> this route, we could go even further and create an optimized module >> format, which is an idea I think we've looked at a little bit in the >> past; there are a few avenues of exploration here which could be >> interesting. > > This could be worth investigating. Tomaž did a prototype of using the JDK JAR filesystem to back the resource loader if it is available; contention did go down but memory footprint went up, and overall the additional indexing and allocation ended up slowing down boot a little, unfortunately (though large numbers of deployments seemed to be faster). Tomaž can elaborate on his findings if he wishes. I had a look in the JAR FS implementation (and its parent class, the ZIP FS implementation, which does most of the hard work), and there are a few things which add overhead and contention that we don't need, like using read/write locks to manage access and modifications (which we don't need) and (synch-based) indexing structures that might be somewhat larger than necessary. They use NIO channels to access the zip data, which is probably OK, but maybe mapped buffers could be better... or worse? They use a synchronized list per JAR file to pool Inflaters; pooling is a hard thing to do right so maybe there isn't really any better option in this case. But in any event, I think a custom extractor still might be a reasonable thing to experiment with. We could resurrect jzipfile or try a different approach (maybe see how well mapped buffers work?). Since we're read-only, any indexes we use can be immutable and thus unsynchronized, and maybe more compact as a result. We can use an unordered hash table because we generally don't care about file order the way that JarFile historically needs to, thus making indexing faster. We could save object allocation overhead by using a specialized object->int hash table that just records offsets into the index for each entry. If we try mapped buffers, we could share one buffer concurrently by using only methods that accept an offset, and track offsets independently. This would let the OS page cache work for us, especially for heavily used JARs. We would be limited to 2GB JAR files, but I don't think that's likely to be a practical problem for us; if it ever is, we can create a specialized alternative implementation for huge JARs.

In Java 9, jimages become an option by way of jlink, which will also be worth experimenting with (as soon as we're booting on Java 9). Brainstorm other ideas here! -- - DML _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

I have a few thoughts that might be of interest. Firstly, I'd be interested to see when you are logging the class name being loaded. If you are logging it in loadClass, you might not be seeing the actual correct load order because that method is ultimately recursive. To get an accurate picture of what order that classes are actually defined - and thus what order you can load them in order to prevent contention on per-class locks within the CL - you should log immediately _after_ defineClass completes for each class. Secondly, while debugging a resource iteration performance problem a user was having with a large number of deployments, I discovered that contention for the lock on JarFile and ZipFile was a primary cause. The workaround I employed was to keep a RAM-based List of the files in the JAR, which can be iterated over without touching the lock. When we're preloading classes, we're definitely going to see this same kind of contention come up, because there's only one lock per JarFile instance so you can only ever read one entry at a time, thus preventing any kind of useful concurrency on a per-module basis. Exploding the files out of the JarFile could expose this contention and therefore might be useful as a test - but it would also skew the results a little because you have no decompression overhead, and creating the separate file streams hypothetically might be somewhat more (or less) expensive. I joked about resurrecting jzipfile (which I killed off because it was something like 20% slower at decompressing entries than Jar/ZipFile) but it might be worth considering having our own JAR extractor at some point with a view towards concurrency gains. If we go this route, we could go even further and create an optimized module format, which is an idea I think we've looked at a little bit in the past; there are a few avenues of exploration here which could be interesting. At some point we also need to see how jaotc might improve things. It probably won't improve class loading time directly, but it might improve the processes by which class loading is done because all the one-off bits would be precompiled. Also it's worth exploring whether the jimage format has contention issues like this. On 05/14/2017 06:36 PM, Stuart Douglas wrote: > When JIRA was being screwy on Friday I used the time to investigate an > idea I have had for a while about improving our boot time performance. > According to Yourkit the majority of our time is spent in class loading. > It seems very unlikely that we will be able to reduce the number of > classes we load on boot (or at the very least it would be a massive > amount of work) so I investigated a different approach. > > I modified ModuleClassLoader to spit out the name and module of every > class that is loaded at boot time, and stored this in a properties file. > I then created a simple Service that starts immediately that uses two > threads to eagerly load every class on this list (I used two threads > because that seemed to work well on my laptop, I think > Runtime.availableProcessors()/4 is probably the best amount, but that > assumption would need to be tested on different hardware). > > The idea behind this is that we know the classes will be used at some > point, and we generally do not fully utilise all CPU's during boot, so > we can use the unused CPU to pre load these classes so they are ready > when they are actually required. > > Using this approach I saw the boot time for standalone.xml drop from > ~2.9s to ~2.3s on my laptop. The (super hacky) code I used to perform > this test is at > https://github.com/wildfly/wildfly-core/compare/master...stuartwdouglas:b... > > I think these initial results are encouraging, and it is a big enough > gain that I think it is worth investigating further. > > Firstly it would be great if I could get others to try it out and see if > they see similar gains to boot time, it may be that the gain is very > system dependent. > > Secondly if we do decide to do this there are two approach that we can > use that I can see: > > 1) A hard coded list of class names that we generate before a release > (basically what the hack already does), this is simplest, but does add a > little bit of additional work to the release process (although if it is > missed it would be no big deal, as ClassNotFoundException's would be > suppressed, and if a few classes are missing the performance impact is > negligible as long as the majority of the list is correct). > > 2) Generate the list dynamically on first boot, and store it in the temp > directory. This would require the addition of a hook into JBoss Modules > to generate the list, but is the approach I would prefer (as first boot > is always a bit slower anyway). > > Thoughts? > > Stuart > > > _______________________________________________ > wildfly-dev mailing list > wildfly-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/wildfly-dev >

On 16. May 2017, at 13:32, J Pai <jai.forums2013(a)gmail.com&gt; wrote: What I have experienced is that for end users, they are mostly interested in seeing their (usually large) deployments show noticeable improvements in deployment time, not necessarily from a cold boot of the server, but when the server is already up and they either want to deploy something new or re-deploy their application.

On May 16, 2017, at 7:41 AM, Heiko Braun <hbraun(a)redhat.com&gt; wrote: On 16. May 2017, at 13:32, J Pai <jai.forums2013(a)gmail.com&gt; wrote: What I have experienced is that for end users, they are mostly interested in seeing their (usually large) deployments show noticeable improvements in deployment time, not necessarily from a cold boot of the server, but when the server is already up and they either want to deploy something new or re-deploy their application. +1 the deployments increase the time until “ready to perform work”. This is the point we should use as a reference. Anything before (i.e. blank WF without deployments) is just marketing IMO. I agree that deployment time is important, but I just want to point out that not all usages of WildFly involve deployments. Examples include proxy servers, static content servers, message brokers, javascript code, transaction managers, and service based applications. -- Jason T. Greene WildFly Lead / JBoss EAP Platform Architect JBoss, a division of Red Hat _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev

On 16. May 2017, at 16:00, David M. Lloyd <david.lloyd(a)redhat.com&gt; wrote: Startup time to "ready" does include the server init; so such an effort isn't a total waste of time in this case. But I agree with your main point. But I think if we can squeeze a bit more speed out of initialization, there's no harm in trying for it. The performance data that comes from this analysis has already been used to target areas that will improve performance for every part of startup, including deployment (maybe substantially).

1) A hard coded list of class names that we generate before a release (basically what the hack already does), this is simplest, but does add a little bit of additional work to the release process (although if it is missed it would be no big deal, as ClassNotFoundException's would be suppressed, and if a few classes are missing the performance impact is negligible as long as the majority of the list is correct).

2) Generate the list dynamically on first boot, and store it in the temp directory. This would require the addition of a hook into JBoss Modules to generate the list, but is the approach I would prefer (as first boot is always a bit slower anyway).

Thoughts? Stuart _______________________________________________ wildfly-dev mailing list wildfly-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/wildfly-dev