// SetCPUProfileRate sets the CPU profiling rate to hz samples per second.
// If hz <= 0, SetCPUProfileRate turns off profiling.
// If the profiler is on, the rate cannot be changed without first turning it off.
//
// Most clients should use the [runtime/pprof] package or
// the [testing] package's -test.cpuprofile flag instead of calling
// SetCPUProfileRate directly.
func SetCPUProfileRate(hz int) {
	// Clamp hz to something reasonable.
	if hz < 0 {

func sigenable(sig uint32) {
}

func sigdisable(sig uint32) {
}

func sigignore(sig uint32) {
}

func setProcessCPUProfiler(hz int32) {
}

func setThreadCPUProfiler(hz int32) {
	// TODO: Enable profiling interrupts.
	getg().m.profilehz = hz
}

// gsignalStack is unused on Plan 9.

(MOVHZreg y:(MOV(H|B)Zreg _)) => y // repeat
(MOVHZreg y:(MOVHBRload _ _)) => y

(MOVHreg y:(MOV(H|B)reg _)) => y // repeat

(MOV(H|HZ)reg y:(MOV(HZ|H)reg x)) => (MOV(H|HZ)reg x)

// W - there are more combinations than these

(MOV(WZ|WZ|WZ|W|W|W)reg y:(MOV(WZ|HZ|BZ|W|H|B)reg _)) => y // repeat
(MOVWZreg y:(MOV(H|W)BRload _ _)) => y

(MOV(W|WZ)reg y:(MOV(WZ|W)reg x)) => (MOV(W|WZ)reg x)

	}
}

// setProcessCPUProfilerTimer is called when the profiling timer changes.
// It is called with prof.signalLock held. hz is the new timer, and is 0 if
// profiling is being disabled. Enable or disable the signal as
// required for -buildmode=c-archive.
func setProcessCPUProfilerTimer(hz int32) {
	if hz != 0 {
		// Enable the Go signal handler if not enabled.
		if atomic.Cas(&handlingSig[_SIGPROF], 0, 1) {
			h := getsig(_SIGPROF)

		}
	}
	for stack, samples := range pprofStacks {
		fmt.Fprintf(os.Stderr, "%s\t%d\n", stack, samples)
	}
}

func cpuHogger(f func(x int) int, y *int, dur time.Duration) {
	// We only need to get one 100 Hz clock tick, so we've got
	// a large safety buffer.
	// But do at least 500 iterations (which should take about 100ms),
	// otherwise TestCPUProfileMultithreaded can fail if only one

	"regexp"
	"runtime"
	"runtime/debug"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"
	_ "unsafe"
)

func cpuHogger(f func(x int) int, y *int, dur time.Duration) {
	// We only need to get one 100 Hz clock tick, so we've got
	// a large safety buffer.
	// But do at least 500 iterations (which should take about 100ms),
	// otherwise TestCPUProfileMultithreaded can fail if only one

	// The runtime routines allow a variable profiling rate,
	// but in practice operating systems cannot trigger signals
	// at more than about 500 Hz, and our processing of the
	// signal is not cheap (mostly getting the stack trace).
	// 100 Hz is a reasonable choice: it is frequent enough to
	// produce useful data, rare enough not to bog down the
	// system, and a nice round number to make it easy to

		<-main_init_done
	}

	// Check whether the profiler needs to be turned on or off; this route to
	// run Go code does not use runtime.execute, so bypasses the check there.
	hz := sched.profilehz
	if gp.m.profilehz != hz {
		setThreadCPUProfiler(hz)
	}

	// Add entry to defer stack in case of panic.
	restore := true
	defer unwindm(&restore)

	if raceenabled {
		raceacquire(unsafe.Pointer(&racecgosync))
	}

	for !prof.signalLock.CompareAndSwap(0, 1) {
		osyield()
	}
	if prof.hz.Load() != hz {
		setProcessCPUProfiler(hz)
		prof.hz.Store(hz)
	}
	prof.signalLock.Store(0)

	lock(&sched.lock)
	sched.profilehz = hz
	unlock(&sched.lock)

	if hz != 0 {
		setThreadCPUProfiler(hz)
	}

	gp.m.locks--
}

000002b0  00 b6 eb cb e3 18 cf 14  03 01 00 01 01 16 03 01  |................|
000002c0  00 30 61 51 84 02 46 3c  10 62 b5 2a a2 8b 4e 2d  |.0aQ..F<.b.*..N-|
000002d0  57 55 26 c5 46 f2 5d a1  f5 20 46 0d 63 fd 48 5a  |WU&.F.].. F.c.HZ|
000002e0  f3 65 90 8c 1a bd 59 6e  5f d1 5c b6 ee 33 49 12  |.e....Yn_.\..3I.|
000002f0  46 ec                                             |F.|
>>> Flow 4 (server to client)