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runtime: observed hot HITM with false-sharing, pointing to GC object #60337

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gavinlichn opened this issue May 22, 2023 · 3 comments
Closed

runtime: observed hot HITM with false-sharing, pointing to GC object #60337

gavinlichn opened this issue May 22, 2023 · 3 comments
Labels
compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.21

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@gavinlichn
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What version of Go are you using (go version)?

$ go version
1.20.4

Does this issue reproduce with the latest release?

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/ansible/.cache/go-build"
GOENV="/home/ansible/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/ansible/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/ansible/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.20.4"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2935128198=/tmp/go-build -gno-record-gcc-switches"

What did you do?

run gRPC benchmark and DeathStarBench hotelReservation

https://github.com/grpc/grpc-go/tree/master/benchmark
https://github.com/delimitrou/DeathStarBench/tree/master/hotelReservation

What did you expect to see?

No significant false-sharing observed

What did you see instead?

Hottest cache line HITM pointing to a false-sharing, and the hottest one contribute ~4% or more HITM

perf-c2c report top HITM as below(shorten output):

`
image

`
@gavinlichn
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Submitted patch for review: https://go-review.googlesource.com/c/go/+/496915

@gopherbot
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Change https://go.dev/cl/496915 mentions this issue: runtime/mgc: add a CacheLinePad to prevent false-sharing

@mknyszek mknyszek changed the title runtime/mgc Observed hot HITM with false-sharing, pointing to GC object runtime: observed hot HITM with false-sharing, pointing to GC object May 22, 2023
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label May 22, 2023
@mknyszek mknyszek added the NeedsFix The path to resolution is known, but the work has not been done. label May 22, 2023
@mknyszek mknyszek added this to the Go1.21 milestone May 22, 2023
@gavinlichn
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Change have been merged:
https://go-review.googlesource.com/c/go/+/496915

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compiler/runtime Issues related to the Go compiler and/or runtime. NeedsFix The path to resolution is known, but the work has not been done.
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Go1.21
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@mknyszek @gopherbot @gavinlichn