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/main/asciidoc/contributing > > On Mon, May 22, 2017 at 6:36 PM Galder Zamarreño <gal...@redhat.com > <mailto:gal...@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 <sa...@infinispan.org > <mailto:sa...@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 > <slask...@redhat.com <mailto:slask...@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%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 > > > > > > _______________________________________________ > > infinispan-dev mailing list > > 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@lists.jboss.org > <mailto:infinispan-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/infinispan-dev > > > _______________________________________________ > infinispan-dev mailing list > 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@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@lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev