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GOMAXPROCS not work #42845

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qiaohao9 opened this issue Nov 26, 2020 · 3 comments
Closed

GOMAXPROCS not work #42845

qiaohao9 opened this issue Nov 26, 2020 · 3 comments
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@qiaohao9
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qiaohao9 commented Nov 26, 2020 •
edited

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

$ go version
go version go1.15.5 linux/amd64

Does this issue reproduce with the latest release?

yes.

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

go env Output
$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/xxx/.cache/go-build"
GOENV="/home/xx/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/xxx/.go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/xxx/.go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/xxx/gRPC-tutorial/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build338536254=/tmp/go-build -gno-record-gcc-switches"

What did you do?

My CPU nums:

$ echo "Threads/core: $(nproc --all)"
Threads/core: 4

Go Playground

What did you expect to see?

It should cost 6s.

What did you see instead?

It cost 3s.
@go101
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go101 commented Nov 26, 2020 •
edited

Why should it cost 6s?

All 8 goroutines are running simultaneously. The result should be unrelated to GOMAXPROCS.

@mpx
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mpx commented Nov 26, 2020 •
edited

GOMAXPROCS limits the number of OS threads used to actively run Goroutines. The goroutines in your example spend almost all their time sleeping (not running) . GOMAXPROCS will make more of a difference if your workers are performing a fixed amount of heavy computation instead.

I'd recommend asking these questions on the Gopher Slack forum, or golang-nuts. This issue tracker is intended for developing the Go toolchain and related projects.

@ALTree
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ALTree commented Nov 26, 2020 •
edited

As it was pointed out, there's no reason to expect the program to take 6s: all the goroutines just sleep for 3s an then the program ends. GOMAXPROCS' value makes no difference here. Closing, since this is not a bug in Go.

@ALTree ALTree closed this as completed Nov 26, 2020
@golang golang locked and limited conversation to collaborators Nov 26, 2021
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@mpx @ALTree @gopherbot @qiaohao9 @go101