Hi Peter, Thank you very much for your updated fix and sorry to be late to reply.
I found that the performance data I posted earlier was wrong because I fetched the latest code before building the JVM with your fix, while I still used older JVM as the base version. The new build picked up JDK-8230020 [1], which reverts JDK-8225670 [2] that degraded performance of SPECjbb2015. Unfortunately, the base version only included [2]... Your new version [3] apparently looks better. I'll update my base JVM and measure the performance of [3]. Regards, Ogata [1] https://bugs.openjdk.java.net/browse/JDK-8230020 [2] https://bugs.openjdk.java.net/browse/JDK-8225670 [3] http://cr.openjdk.java.net/~plevart/jdk-dev/8229871_Method.methodAccessor/webrev.01/ Peter Levart <peter.lev...@gmail.com> wrote on 2019/10/24 06:09:54: > From: Peter Levart <peter.lev...@gmail.com> > To: Kazunori Ogata <oga...@jp.ibm.com> > Cc: core-libs-dev@openjdk.java.net > Date: 2019/10/24 06:10 > Subject: [EXTERNAL] Re: RFR: JDK-8229871: Improve performance of > Method.copy() and leafCopy() > > Hi Ogata, > > I finally managed to find some time to experiment with this. To measure > invocation performance I created the following JMH benchmark [1]. It > measures the invocation speed of instance and static methods using either: > - direct invocation (bytecodes) > - invocation via constant Method instance > - invocation via variable Method instance > > Here are the results using unmodified JDK 14 build (baseline): > > Benchmark Mode Cnt Score > Error Units > ReflectionSpeedBenchmark.instanceDirect avgt 10 2.272 ± > 0.002 ns/op > ReflectionSpeedBenchmark.instanceReflectiveConst avgt 10 16.609 ± > 0.162 ns/op > ReflectionSpeedBenchmark.instanceReflectiveVar avgt 10 16.715 ± > 0.163 ns/op > ReflectionSpeedBenchmark.staticDirect avgt 10 2.275 ± > 0.012 ns/op > ReflectionSpeedBenchmark.staticReflectiveConst avgt 10 16.351 ± > 0.330 ns/op > ReflectionSpeedBenchmark.staticReflectiveVar avgt 10 16.259 ± > 0.196 ns/op > > Your webrev.04 [2] has a slight (~ 6%) improvement for constant Method > instance (i.e. assigned to static final field): > > Benchmark Mode Cnt Score > Error Units > ReflectionSpeedBenchmark.instanceDirect avgt 10 2.273 ± > 0.003 ns/op > ReflectionSpeedBenchmark.instanceReflectiveConst avgt 10 15.628 ± > 0.115 ns/op > ReflectionSpeedBenchmark.instanceReflectiveVar avgt 10 16.706 ± > 0.144 ns/op > ReflectionSpeedBenchmark.staticDirect avgt 10 2.277 ± > 0.008 ns/op > ReflectionSpeedBenchmark.staticReflectiveConst avgt 10 15.285 ± > 0.109 ns/op > ReflectionSpeedBenchmark.staticReflectiveVar avgt 10 16.600 ± > 0.222 ns/op > > Now I have prepared another variant [3] that replaces > DelegatingMethodAccessorImpl with SlowFastMethodAccessorImpl and > produces the following result: > > Benchmark Mode Cnt Score > Error Units > ReflectionSpeedBenchmark.instanceDirect avgt 10 2.371 ± > 0.027 ns/op > ReflectionSpeedBenchmark.instanceReflectiveConst avgt 10 7.161 ± > 0.066 ns/op > ReflectionSpeedBenchmark.instanceReflectiveVar avgt 10 16.501 ± > 0.154 ns/op > ReflectionSpeedBenchmark.staticDirect avgt 10 2.373 ± > 0.017 ns/op > ReflectionSpeedBenchmark.staticReflectiveConst avgt 10 6.971 ± > 0.103 ns/op > ReflectionSpeedBenchmark.staticReflectiveVar avgt 10 15.893 ± > 0.110 ns/op > > This is more than twice as fast as the baseline for constant Method > instances while not degrading performance for variable Method instances. > > > [1] http://cr.openjdk.java.net/~plevart/jdk-dev/8229871_Method.methodAccessor/ReflectionSpeedBenchmark.java > [2] http://cr.openjdk.java.net/~ogatak/8229871/webrev.04/ > [3] http://cr.openjdk.java.net/~plevart/jdk-dev/8229871_Method.methodAccessor/webrev.01/ > > > Could you spin this one [3] on your SPECjbb2015 benchmark to see if it > still performs favorably? > > > Regards, Peter > > On 10/11/19 12:17 PM, Kazunori Ogata wrote: > > Hi Peter, > > > > Thank you for the comment and suggestion of the fix. > > > > I tried to pick up your change w.r.t. methodAccessor: > > https://urldefense.proofpoint.com/v2/url? > u=https-3A__cr.openjdk.java.net_-7Eogatak_8229871_webrev. > 04_&d=DwIDaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=-xRlUE3M_VEQ_pLDsVNMsIneJ7tKig8ElUy8vmAQoUM&e= > > > > > > Regarding micro benchmark, my original motivation of this change is to > > improve performance of Class.getMethods(), which calls Method.copy() for > > each declared method to create a copy of Method[]. > > > > I measured my simple microbench: > > https://urldefense.proofpoint.com/v2/url? > u=https-3A__cr.openjdk.java.net_-7Eogatak_8229871_GetMethodsBench.java&d=DwIDaQ&c=jf_iaSHvJObTbx- > siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=Phaibyh6EWjUKos14T7aQfBzSGcH4stxqnhQFkEZsp4&e= > > > > Base code: Elapsed time = 4808 ms > > webrev.01: Elapsed time = 4536 ms (+ 6%) > > webrev.02: Elapsed time = 2331 ms (+106%) > > webrev.04: Elapsed time = 3746 ms (+ 28%) > > > > I'll measure larger benchmark and try to think if we can reduce the > > overhead of memory barrier. > > > > > > Regards, > > Ogata > > > > > > Peter Levart <peter.lev...@gmail.com> wrote on 2019/10/09 16:44:13: > > > >> From: Peter Levart <peter.lev...@gmail.com> > >> To: Kazunori Ogata <oga...@jp.ibm.com>, core-libs-dev@openjdk.java.net > >> Date: 2019/10/09 16:44 > >> Subject: [EXTERNAL] Re: RFR: JDK-8229871: Improve performance of > >> Method.copy() and leafCopy() > >> > >> Hi Ogata, > >> > >> May I just add that volatile field ensured that MethodAccessor object > > was > >> correctly published. DelegatingMethodAccessortImpl is not safe to be > >> published via data race because it contains plain `delegate` field > >> initialized in the constructor. In addition, the object that is first > >> assigned to that field is NativeMethodAccessorImpl which has plain > >> `parent` field. You can get NPE when invoking the Method.invoke from > >> multuiple threads if Method.methodAccessor is not volatile. > >> > >> In addition, It would be nice to have two microbenchmarks exercising: > >> a) Method copy performance > >> b) Method invocation performance > >> > >> Regards, Peter > >> > >> P.S. When exploring the possibility of an alternative MethodAccessor > >> implementation (using MethodHandle(s)): > >> > >> > > https://urldefense.proofpoint.com/v2/url? > u=http-3A__cr.openjdk.java.net_-7Eplevart_jdk-2Ddev_6824466-5FMHReflectionAccessors_&d=DwIDaQ&c=jf_iaSHvJObTbx- > siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=LKR_2z3fvXB0IYUryijzgd-jH6wG3Mr2UmiOMKviFGU&e= > >> webrev.00.2/ > >> > >> ...I found out that it was possible to re-arrange the play between > >> DelegatingMethodAccessorImpl, NativeMethodAccessorImpl and generated > >> MethodAccessor in such a way that the DelegatingMethodAccessortImpl > >> becomes safe to be published via data race. This allowed for > >> Method.methodAccessor field to become plain field. In addition this > > field > >> can be made @Stable which further optimizes access to MethodAccessor > >> instance when Method instance can be constant-folded, which showed in > >> special microbenchmarks. > >> > >> So perhaps you could try to use above implementation (just changes to > >> DelegatingMethodAccessorImpl, NativeMethodAccessorImpl and part of > >> Reflection factory but without MH* stuff) and measure it against current > >> and your implementation (which as shown above has a data-race flaw). > >> On 10/8/19 12:23 PM, Kazunori Ogata wrote: > >> Hi all, > >> > >> I posted two changes and got reply that performance evaluation is > > needed. > >> I found that making Method.methodAccessor non-volatile (webrev.02) is > >> better than avoid copying methodAccessor value when it is null > >> (webrev.01), as shown below. > >> > >> So I'd like to ask review of the former change. I updated weberv using > >> the latest code base (though there was no difference from webrev.02): > >> > >> Webrev: https://urldefense.proofpoint.com/v2/url? > u=http-3A__cr.openjdk.java.net_-7Eogatak_8229871_webrev. > 03_&d=DwIDaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=xm_iw74CmqAabV2cctZfI75t28_DCXP9VFVjHcnQXp4&e= > >> > >> Bug: https://urldefense.proofpoint.com/v2/url? > u=https-3A__bugs.openjdk.java.net_browse_JDK-2D8229871&d=DwIDaQ&c=jf_iaSHvJObTbx- > siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=bzRkFq845mYFriH7TirkzA4JzG0m47x09kebpHfMgTw&e= > >> > >> > >> For this performance evaluation, I calculated 75 percentile of 9 runs of > >> SPECjbb2015 and 60 percentile of 50 runs of DaCapo to omit outliers. I > >> bound a JVM to a NUMA node and set the number of GC threads to the same > > as > >> the number of physical cores. These tuning reduced run-to-run > > fluctuation > >> on POWER (as usual...). > >> > >> SPECjbb2015: > >> webrev.02: critical jOPS +1.6%, max jOPS +0.2% > >> webrev.01: critical jOPS +0.4%, max jOPS +0.2% > >> > >> > >> For DaCapo, some benchmark still improved performance and some degraded, > >> but the geometric mean of all benchmarks were small: > >> weberv.02: +0.3% > >> weberv.01: +0.2% > >> > >> The difference of improvement/degradation between the two changes in > > each > >> benchmark were less than 0.8%. > >> > >> The range of improvement/degradation in each benchmark were: > >> webrev.02: between +2.4% and -1.0% > >> webrev.01: between +1.6% and -1.8% > >> > >> > >> So I think webrev.02 (i.e., making methodAccessor non-volatile) is a > > good > >> change, since it improved SPECjbb critical jOPS by 1.6%. > >> > >> > >> Regards, > >> Ogata > >> > >> > >> Kazunori Ogata/Japan/IBM wrote on 2019/08/27 15:41:39: > >> > >> From: Kazunori Ogata/Japan/IBM > >> To: Mandy Chung <mandy.ch...@oracle.com> > >> Cc: core-libs-dev@openjdk.java.net > >> Date: 2019/08/27 15:41 > >> Subject: Re: RFR: JDK-8229871: Improve performance of Method.copy() and > >> leafCopy() > >> Hi Mandy, > >> > >> Let me post interim results of the performance evaluation, though I'm > >> still measuring benchmarks and analyzing them. > >> > >> For SPECjbb2015, skipping storing null (webrev.01) was faster than > >> making > >> methodAccessor non-volatile (webrev.02). The improvements of each of > >> the > >> patches in maxJOPS/criticalJOPS were 2.6%/3.9% and 1.8%/2.9%, > >> respectively. This is only an average of six runs. > >> > >> For DaCapo, the results were mixed. In some benchmark, both of the > >> changes degraded performance. In some others, webrev.01 was better, but > > > >> weberv.02 was better in some others. > >> > >> I'll continue evaluation, but it is helpful if you could give me some > >> hints on why webrev.01 can be better than webrev.02 in SPECjbb2015. > >> > >> Regards, > >> Ogata > >> > >> Kazunori Ogata/Japan/IBM wrote on 2019/08/21 20:02:41: > >> > >> From: Kazunori Ogata/Japan/IBM > >> To: Mandy Chung <mandy.ch...@oracle.com> > >> Cc: core-libs-dev@openjdk.java.net > >> Date: 2019/08/21 20:02 > >> Subject: Re: RFR: JDK-8229871: Improve performance of Method.copy() > >> and leafCopy() > >> Hi Mandy, > >> > >> Thank you for reviewing the webrev. I updated it to add a space after > >> "if" and also put four spaces for indentation (it was three). > >> > >> https://urldefense.proofpoint.com/v2/url? > u=http-3A__cr.openjdk.java.net_-7Eogatak_8229871_webrev. > 01_&d=DwIDaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=qLT9k5xsheWZfU7ocimSbEMANQDnelEUqqiR5X-Zio4&e= > >> > >> Thank you so much for checking the history of fieldAccessor. I was > >> surprised that fieldAccessor was made non-volatile in JDK5, but > >> methodAccessor was left as volatile for 15 years after that... > >> > >> I agree we need benchmark data. My simple micro benchmark that > >> repeats > >> invoking Class.getMethods() improved performance by 70% when it made > >> non- > >> volatile (as shown in the following webrev). I'll try to run larger > >> benchmarks, such as SPECjbb2015, to see real impact. > >> > >> https://urldefense.proofpoint.com/v2/url? > u=http-3A__cr.openjdk.java.net_-7Eogatak_8229871_webrev. > 02_&d=DwIDaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=aq50ONJW0fK7CBk1upVkJekAbRrDsZygPkWrjL_sM4I&e= > >> > >> Regards, > >> Ogata > >> > >> Mandy Chung <mandy.ch...@oracle.com> wrote on 2019/08/21 01:21:42: > >> > >> From: Mandy Chung <mandy.ch...@oracle.com> > >> To: Kazunori Ogata <oga...@jp.ibm.com> > >> Cc: core-libs-dev@openjdk.java.net > >> Date: 2019/08/21 01:21 > >> Subject: [EXTERNAL] Re: RFR: JDK-8229871: Imporve performance of > >> Method.copy() and leafCopy() > >> > >> Hi Ogata, > >> > >> The patch looks okay. Nit: please add a space between if and (. > >> > >> About volatile methodAccessor field, I checked the history. Both > >> fieldAccessor and methodAccessor were started as volatile and the > >> fieldAccessor declaration was updated due to JDK-5044412. As you > >> observe, I think the methodAccessor field could be made > >> non-volatile. > >> OTOH that might impact when it's inflated to spin bytecode for this > >> method invocation. I don't know how importance to keep its volatile > >> vs > >> non-volatile in practice without doing benchmarking/real application > >> testing. > >> > >> Mandy > >> > >> On 8/19/19 2:51 AM, Kazunori Ogata wrote: > >> Hi, > >> > >> May I have review for "JDK-8229871: Imporve performance of > >> Method.copy() > >> and leafCopy()"? > >> > >> Method.copy() and leafCopy() creates a copy of a Method object > >> with > >> sharing MethodAccessor object. Since the methodAccessor field is a > >> volatile variable, copying this field needs memory fence to ensure > >> the > >> field is visible to all threads on the weak memory platforms such > >> as POWER > >> and ARM. > >> > >> When the methodAccessor of the root object is null (i.e., not > >> initialized > >> yet), we do not need to copy the null value because this field of > >> the > >> copied object has been initialized to null in the constructor. We > >> can > >> reduce overhead of the memory fence only when the root's > >> methodAccessor is > >> non-null. This change improved performance by 5.8% using a micro > >> benchmark > >> that repeatedly invokes Class.getMethods(). > >> > >> Bug: https://urldefense.proofpoint.com/v2/url? > u=https-3A__bugs.openjdk.java.net_browse_JDK-2D8229871&d=DwIDaQ&c=jf_iaSHvJObTbx- > siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=bzRkFq845mYFriH7TirkzA4JzG0m47x09kebpHfMgTw&e= > >> > >> Webrev: https://urldefense.proofpoint.com/v2/url? > u=http-3A__cr.openjdk.java.net_-7Eogatak_8229871_webrev. > 00_&d=DwIDaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=p- > FJcrbNvnCOLkbIdmQ2tigCrcpdU77tlI2EIdaEcJw&m=kWMN3Fiqhqdlc9lMvgHDA1VViBz9r2Eb- > K9uCUrU_Yw&s=lGQy-Xy0ofp8d551jCUZdwmZ_OD4sXsMaoRKWzwer4o&e= > >> > >> > >> By the way, why Method.methodAccessor is volatile, while > >> Field.fieldAccessor and Field.overrideFieldAccessor are not > >> volatile? I > >> know the use of volatile reduces probability of creating > >> duplicated method > >> accessor, but the chance still exists. I couldn't find the > >> difference > >> between Method and Field classes to make Method.methodAccessor > >> volatile. > >> If we can make it non-volatile, it is more preferable than a quick > >> hack > >> above. > >> > >> > >> Regards, > >> Ogata > >> > >> > >> > > > >
