RFR: 8276662: Scalability bottleneck in SymbolTable::lookup_common() [v2]

[Derek White]

On Fri, 19 Nov 2021 04:12:33 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Derek White has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix scalability with THREAD_LOCAL
>
> I did a quick check of the latest patch. Small start-up runs like this are susceptible to effects of dynamic frequency scaling due to CPU heat, so I interleaved the runs just to be safe:
> 
> 
> for i in 1 2 3 4 5; do
>     for v in old new; do
>         echo $v.$i.txt
>         perf stat -o $v.$i.txt -r 500 ./jdk_$v/bin/java \
>              -Xmx128m -Xshare:on -version 2> /dev/null
>     done
> done
> 
> 
> old.1.txt:          0.044077 +- 0.000425 seconds time elapsed  ( +-  0.96% )
> old.2.txt:          0.043140 +- 0.000385 seconds time elapsed  ( +-  0.89% )
> old.3.txt:          0.044393 +- 0.000415 seconds time elapsed  ( +-  0.93% )
> old.4.txt:          0.043779 +- 0.000407 seconds time elapsed  ( +-  0.93% )
> old.5.txt:          0.043221 +- 0.000390 seconds time elapsed  ( +-  0.90% )
> geomean = 0.043719
> 
> new.1.txt:          0.043791 +- 0.000405 seconds time elapsed  ( +-  0.93% )
> new.2.txt:          0.042716 +- 0.000364 seconds time elapsed  ( +-  0.85% )
> new.3.txt:          0.043203 +- 0.000382 seconds time elapsed  ( +-  0.88% )
> new.4.txt:          0.043437 +- 0.000398 seconds time elapsed  ( +-  0.92% )
> new.5.txt:          0.043012 +- 0.000382 seconds time elapsed  ( +-  0.89% )
> geomean = 0.043230
> 
> 
> So at least on my machine (10 year old dual socket Xeon/Sandybridge) the patch doesn't seem to introduce any regression.

@iklam, we've seen 5-15% improvement in serialization benchmarks on CascadeLake/IceLake systems, and almost 2x improvement on mutli-socket systems with more cores.

-------------

PR: https://git.openjdk.java.net/jdk/pull/6400