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Change the instruction used for a pause on arm64 #10118
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While the yield instruction conseptually sounds correct on most platforms it is a simple nop that doesn't delay the execution anywhere close to what an x86 pause instruction does. In other projects with spin-wait loops an isb has been observed to be much closer to the x86 behavior. On a Graviton3 system the following test improves on average by 2x with this change averaged over 20 runs: ./db_bench -benchmarks=fillrandom -threads=64 -batch_size=1 -memtablerep=skip_list -value_size=100 --num=100000 level0_slowdown_writes_trigger=9999 -level0_stop_writes_trigger=9999 -disable_auto_compactions --max_write_buffer_number=8 -max_background_flushes=8 --disable_wal --write_buffer_size=160000000 --block_size=16384 --allow_concurrent_memtable_write -compression_type none
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@siying any chance you could review this one as well? |
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Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks! |
@siying has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
@AGSaidi has updated the pull request. You must reimport the pull request before landing. |
@siying has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
While the yield instruction conseptually sounds correct on most platforms it is
a simple nop that doesn't delay the execution anywhere close to what an x86
pause instruction does. In other projects with spin-wait loops an isb has been
observed to be much closer to the x86 behavior.
On a Graviton3 system the following test improves on average by 2x with this
change averaged over 20 runs: