[infinispan-dev] CHM or CHMv8?

[Sanne Grinovero]

Why not. Only doubt I'd have is that other usages of the CHM are - I guess
- services registry and similar configuration tools, for which write
performance is irrelevant: your test measured puts, are there drawbacks on
gets or memory usage?

Recently you changed all (most?) CHM creations to use a consistent factory,
maybe we could improve on that by actually using a couple of factories
which differentiate on the intended usage of the CHM: for example some maps
who change very infrequently - mostly during boot or reconfiguration, maybe
even topology change - could be better served by a non concurrent structure
using copy-on-wrtite.

Sanne
On 19 Apr 2013 08:48, "Dan Berindei" <dan.berindei at gmail.com> wrote:

> +1 to make CHMv8 the default on JDK6 and JDK7
>
> But I'm not convinced we should make it the default for JDK8 - even though
> we don't know exactly what we're getting with the JDK's implementation.
>
>
> On Fri, Apr 19, 2013 at 5:39 AM, David M. Lloyd <david.lloyd at redhat.com>wrote:
>
>> On 04/18/2013 09:35 PM, Manik Surtani wrote:
>> > Guys,
>> >
>> > Based on some recent micro benchmarks I've been doing, I've seen:
>> >
>> > MapStressTest configuration: capacity 100000, test running time 60
>> seconds
>> > Testing mixed read/write performance with capacity 100,000, keys
>> 300,000, concurrency level 32, threads 12, read:write ratio 0:1
>> > Container CHM           Ops/s 21,165,771.67  Gets/s       0.00  Puts/s
>> 21,165,771.67  HitRatio     100.00  Size    262,682  stdDev 77,540.73
>> > Container CHMV8         Ops/s 33,513,807.09  Gets/s       0.00  Puts/s
>> 33,513,807.09  HitRatio     100.00  Size    262,682  stdDev 77,540.73
>> >
>> > So under high concurrency (12 threads, on my workstation with 12
>> hardware threads - so all threads are always working), we see that
>> Infinispan's CHMv8 implementation is 50% faster than JDK6's CHM
>> implementation when doing puts.
>> >
>> > We use a fair number of CHMs all over Infinispan's codebase.  By
>> default, these are all JDK-provided CHMs.  But we have the option to switch
>> to our CHMv8 implementation by passing in
>> -Dinfinispan.unsafe.allow_jdk8_chm=true.
>> >
>> > The question is, should this be the default?  Thoughts, opinions?
>>
>> The JDK's concurrency code - especially CHM - changes all the time.
>> You'd be very well-served, in my opinion, to go with something like
>> CHMv8 just because you could be so much more sure that you'll have more
>> consistent (and possibly better, but definitely more consistent)
>> performance across all JVMs, instead of being at the mercy of whatever
>> particular implementation happens to run on whatever JVM.
>>
>>
>> --
>> - DML
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>
>
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