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

$ go version
go version go1.21.1 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

Debian 12.1 with an i7-1165g7.

$ go env
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/alex/.cache/go-build'
GOENV='/home/alex/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/alex/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/alex/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/golang/go-1.21.1'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/golang/go-1.21.1/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.21.1'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/alex/repaste_mini/go.mod'
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 -ffile-prefix-map=/tmp/go-build2302350423=/tmp/go-build -gno-record-gcc-switches'

What did you do?

I compiled and executed the snippet of code below.

package main

import (
	"math"
	"math/rand"
	"runtime"
	"time"
)

const (
	timeLimit   = 1  // timeout in minutes
	timeSegment = 10 // sample rate in seconds
)

func Repaste(upTo int, done chan any) {
	for i := 0; i < upTo; i++ {
		select {
		case <-done:
			break
		default:
		}
		_ = math.Sqrt(rand.Float64())
	}
}

func main() {
	lim := runtime.NumCPU()
	done := make(chan any, lim)
	for i := 0; i < lim; i++ {
		go Repaste(math.MaxInt, done)
	}

	runTime := timeLimit * 60 // convert to seconds
	for i := 0; i < runTime; i += timeSegment {
		time.Sleep(timeSegment * time.Second)
	}

	for i := 0; i < lim; i++ {
		done <- i
	}

}

What did you expect to see?

I expected to see all 4 cores / 8 threads hit 4.1GHz during turbo boost.
NOTE: I am able to get this all-core clock speed with the exact same code snippet but built with Go 1.20.8 on the same machine, so I know it isn't a hardware issue like hitting thermal/power limits.

What did you see instead?

All cores / threads were at 100% utilization but only peaked at 3.6GHz.

It is also worth mentioning that I have tried other variations of "load" besides math.Sqrt(), such as just primitive arithmetic expressions, so this would not reflect a regression in the math package, the issue lies elsewhere.