runtime: Simple HTTP server causes high thread count on macOS Monterey

[chrisprobst]

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

$ go version
go version go1.17.2 darwin/arm64

Does this issue reproduce with the latest release?

Cannot test 1.17.3 currently.

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

Apple M1 Max MacBook Pro 16.

go env Output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/XXX/Library/Caches/go-build"
GOENV="/Users/XXX/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/XXX/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/XXX/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/homebrew/Cellar/go/1.17.2/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/homebrew/Cellar/go/1.17.2/libexec/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.17.2"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/06/1d1vrn6541133ymsn2s2vwvw0000gn/T/go-build3566489552=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

1. Spawn a simple http server

package main

import "net/http"

func main() {
	http.HandleFunc("/", func(rw http.ResponseWriter, r *http.Request) {
		rw.WriteHeader(200)
	})
	if err := http.ListenAndServe(":8080", nil); err != nil {
		panic(err)
	}
}

2. Run some requests against it
   wrk -c500 -d10 -t1 http://localhost:8080

What did you expect to see?

With the previous macOS versions (as with every other OS I've tested lately) the app uses a couple of threads (usually around 8-12 all the time).

What did you see instead?

Thread count goes very high and never drops:

[heschi]

cc @neild

[odeke-em]

@chrisprobst thank you for the report and happy new year to you and to you @heschi :-)

@chrisprobst, I am on MacOS Monterrey as well and I've failed to reproduce this problem with various values of -c and -t in ranges too

go1.17.5

go-49679-1.17.5.mp4

go1.18

go-49679-1.18.mp4

@chrisprobst can you reproduce this even right now?

[chrisprobst]

@odeke-em Hi, thanks for checking. I am running on M1 Max CPU and 12.0.1 (so still not updated to 12.1, will do shortly). The problem exists both for 1.17.5 and 1.18Beta1. Will notify you when updated to 12.1.

[chrisprobst]

@odeke-em I've updated to 12.1, same results. Can you reproduce with an M1 Max? I have the feeling it is linked to the M1 architecture. But the problem is still present. With Rust, etc. this problem is not present so it is related to thread management of Go probably.

[odeke-em]

Interesting, thank you @chrisprobst! Let me kindly ask a colleague @kirbyquerby who has an M1 to try to reproduce it, and then I shall go purchase an M1 Pro or M1 Max computer tomorrow morning too and try to reproduce it then debug it.

[kirbyquerby]

Here's my results with Go 1.17 on Big Sur and then after updating to Monterey. The number of threads seemed to increase (peak 22 on Big Sur -> 32 on Monterey) but didn't balloon to large values like in the OP.

Big Sur results:
https://drive.google.com/file/d/1IXAvDKuBSsuCX3GfpXCju2gKljn-sarV/view?usp=sharing

Monterey results:
https://drive.google.com/file/d/1GIg5I7rsUc19cp0aOvpnbXw7SHZX3y1-/view?usp=sharing

`go env` output

$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN="/Users/nathan/go/bin"
GOCACHE="/Users/nathan/Library/Caches/go-build"
GOENV="/Users/nathan/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/nathan/go/pkg/mod"
GONOPROXY="github.com/orijtech/*"
GONOSUMDB="github.com/orijtech/*"
GOOS="darwin"
GOPATH="/Users/nathan/go"
GOPRIVATE="github.com/orijtech/*"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.17"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/h5/hnjslbmn52zb11xzqg9dmy7w0000gn/T/go-build2021634348=/tmp/go-build -gno-record-gcc-switches -fno-common"

Let me know if I can help test anything else :D

[chrisprobst]

I will record a video as soon as I can. In my example, the Threads go up to the hundreds.

[chrisprobst]

1.17.5.mp4

[chrisprobst]

@odeke-em @kirbyquerby As you can see, the threads go extremely high. It's now macOS 12.1 and Go 1.17.5 (1.18beta1 is the same).

[chrisprobst]

@kirbyquerby I noticed that you are using an M1, maybe it's related to M1 Max? The Low-Power cores are different, maybe it is somehow affected by this?

[davecheney]

Is this possibly related to some security software on that laptop; previously users have reported that “anti virus” software from semantic and McAfee tend to have detrimental impact on macOS computers.