Repository: go
Issue: runtime:  pointer assignment in tight loop cause long STW
Labels: NeedsInvestigation,compiler/runtime

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### What version of Go are you using (`go version`)?

<pre>
$ go version
go version go1.20.2 linux/amd64
</pre>

### Does this issue reproduce with the latest release?

Yes

### What operating system and processor architecture are you using (`go env`)?

<details><summary><code>go env</code> Output</summary><br><pre>
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/zgy/.cache/go-build"
GOENV="/home/zgy/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/zgy/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/zgy/go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn,direct"
GOROOT="/home/zgy/00.Tools/stablego/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/zgy/00.Tools/stablego/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.20.2"
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-build2002358002=/tmp/go-build -gno-record-gcc-switches"

</pre></details>

### What did you do?
```go
package main

import (
	"runtime"
	"time"
)

var a = [1000]*int{}

func Func1() {
	var b [1000]*int
	for a[0] == nil {
		a = b
	}
}

func main() {
	go Func1()
	ticker := time.NewTicker(time.Second)
	for range ticker.C {
		runtime.GC()
	}
}
```

Use `go build` to build this single file program. 
And use `export GODEBUG=gctrace=1` to enable gctrace.
Then just excute it.
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If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on go.dev/play is best.
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### What did you expect to see?

The STW time of GC should in normal range. Maybe microseconds to milliseconds.

### What did you see instead?
<pre>
./main 
gc 1 @1.001s 24%: 328+4201+1363 ms clock, 5259+0/0.13/0+21812 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
gc 2 @6.894s 39%: 48+3432+3799 ms clock, 768+0/0.10/0+60788 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
gc 3 @14.173s 41%: 389+838+673 ms clock, 6231+0/0.13/0+10774 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
gc 4 @16.075s 49%: 2399+319+544 ms clock, 38386+0/0.12/0+8716 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
gc 5 @19.339s 38%: 413+7188+725 ms clock, 6621+0/0.10/0+11607 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
gc 6 @27.667s 40%: 15+145+1200 ms clock, 243+0/0.091/0+19212 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
gc 7 @29.028s 45%: 1281+450+1298 ms clock, 20501+0/0.11/0+20773 ms cpu, 0->0->0 MB, 4 MB goal, 0 MB stacks, 0 MB globals, 16 P (forced)
</pre>

Actually, The second STW during GC is about one second. I have even observed it will be several minutes.

It seems that this may be related to #36365 . There is a task "Make large pointer-full memmoves/memclrs preemptible" in it. But it seems that it is no more update about it.