On Tue, 1 Jul 2025 06:41:32 GMT, Xiaohong Gong <xg...@openjdk.org> wrote:
>> Ping again! Thanks in advance! > >> @XiaohongGong I'm a little busy at the moment, and soon going on a summer >> vacation, so I cannot promise a full review soon. Feel free to ask someone >> else to have a look. >> >> I quickly looked through your new benchmark results you published after >> integration of #25539. There seem to still be a few cases where `Gain < 1`. >> Especially: >> >> ``` >> GatherOperationsBenchmark.microShortGather512_MASK 256 thrpt 30 >> ops/ms 11587.465 10674.598 0.92 >> GatherOperationsBenchmark.microShortGather512_MASK 1024 thrpt 30 >> ops/ms 2902.731 2629.739 0.90 >> GatherOperationsBenchmark.microShortGather512_MASK 4096 thrpt 30 >> ops/ms 741.546 671.124 0.90 >> ``` >> >> and >> >> ``` >> GatherOperationsBenchmark.microShortGather256_MASK 256 thrpt 30 >> ops/ms 11339.217 10951.141 0.96 >> GatherOperationsBenchmark.microShortGather256_MASK 1024 thrpt 30 >> ops/ms 2840.081 2718.823 0.95 >> GatherOperationsBenchmark.microShortGather256_MASK 4096 thrpt 30 >> ops/ms 725.334 696.343 0.96 >> ``` >> >> and >> >> ``` >> GatherOperationsBenchmark.microByteGather512_MASK 64 thrpt 30 >> ops/ms 50588.210 48220.741 0.95 >> ``` >> >> Do you know what happens in those cases? > > Thanks for your input! Yes, I spent some time making an analysis on these > little regressions. Seems there are the architecture HW influences like the > cache miss or code alignment. I tried with a larger loop alignment like 32, > and the performance will be improved and regressions are gone. Since I'm not > quite familiar with X86 architectures, I'm not sure of the exact point. Any > suggestions on that? @XiaohongGong Maybe someone from Intel (@jatin-bhateja @sviswa7) can help you with the x86 specific issues. You could always use hardware counters to measure cache misses. Also if the vectors are not cache-line aligned, there may be split loads or stores. Also that can be measured with hardware counters. Maybe the benchmark needs to be improved somehow, to account for issues with alignment. ------------- PR Comment: https://git.openjdk.org/jdk/pull/25138#issuecomment-3022132271
