JIT: add ability to pad profile counters and adjust scalable count th…#91081
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…reshold * `DOTNET_JitCounterPadding`: adds the ability to pad profile counters by some number of counter-sized slots, to mitigate the effects of false sharing. For example with 64 bit counters, setting `DOTNET_JitCounterPadding=8` means each counter is now on its own cache line (for xarch). * `DOTNET_TieredPGO_ScalableCountThreshold`: adds the ability to alter the scalable profile counter's threshold for switching to approximate counting. Defaults to 13 which means profile counts are exact up to 2^13 = 8192 and approximate above that. Lower values will reduce the volume of counter updates (also mitigating false sharing impact) but make the counts more approximate.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue Details…reshold
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These may prove useful someday. @EgorBo PTAL |
Co-authored-by: Jakob Botsch Nielsen <Jakob.botsch.nielsen@gmail.com>
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DOTNET_JitCounterPadding: adds the ability to pad profile counters by some number of counter-sized slots, to mitigate the effects of false sharing. For example with 64 bit counters, settingDOTNET_JitCounterPadding=8means each counter is now on its own cache line (for xarch).DOTNET_TieredPGO_ScalableCountThreshold: adds the ability to alter the scalable profile counter's threshold for switching to approximate counting. Defaults to 13 which means profile counts are exact up to 2^13 = 8192 and approximate above that. Lower values will reduce the volume of counter updates (also mitigating false sharing impact) but make the counts more approximate.