threadpprof.go

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build !plan9 && !windows
     6  // +build !plan9,!windows
     7  
     8  package main
     9  
    10  // Run a slow C function saving a CPU profile.
    11  
    12  /*
    13  #include <stdint.h>
    14  #include <time.h>
    15  #include <pthread.h>
    16  
    17  int threadSalt1;
    18  int threadSalt2;
    19  
    20  void cpuHogThread() {
    21  	int foo = threadSalt1;
    22  	int i;
    23  
    24  	for (i = 0; i < 100000; i++) {
    25  		if (foo > 0) {
    26  			foo *= foo;
    27  		} else {
    28  			foo *= foo + 1;
    29  		}
    30  	}
    31  	threadSalt2 = foo;
    32  }
    33  
    34  void cpuHogThread2() {
    35  }
    36  
    37  struct cgoTracebackArg {
    38  	uintptr_t  context;
    39  	uintptr_t  sigContext;
    40  	uintptr_t* buf;
    41  	uintptr_t  max;
    42  };
    43  
    44  // pprofCgoThreadTraceback is passed to runtime.SetCgoTraceback.
    45  // For testing purposes it pretends that all CPU hits in C code are in cpuHog.
    46  void pprofCgoThreadTraceback(void* parg) {
    47  	struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
    48  	arg->buf[0] = (uintptr_t)(cpuHogThread) + 0x10;
    49  	arg->buf[1] = (uintptr_t)(cpuHogThread2) + 0x4;
    50  	arg->buf[2] = 0;
    51  }
    52  
    53  static void* cpuHogDriver(void* arg __attribute__ ((unused))) {
    54  	while (1) {
    55  		cpuHogThread();
    56  	}
    57  	return 0;
    58  }
    59  
    60  void runCPUHogThread(void) {
    61  	pthread_t tid;
    62  	pthread_create(&tid, 0, cpuHogDriver, 0);
    63  }
    64  */
    65  import "C"
    66  
    67  import (
    68  	"context"
    69  	"fmt"
    70  	"os"
    71  	"runtime"
    72  	"runtime/pprof"
    73  	"time"
    74  	"unsafe"
    75  )
    76  
    77  func init() {
    78  	register("CgoPprofThread", CgoPprofThread)
    79  	register("CgoPprofThreadNoTraceback", CgoPprofThreadNoTraceback)
    80  }
    81  
    82  func CgoPprofThread() {
    83  	runtime.SetCgoTraceback(0, unsafe.Pointer(C.pprofCgoThreadTraceback), nil, nil)
    84  	pprofThread()
    85  }
    86  
    87  func CgoPprofThreadNoTraceback() {
    88  	pprofThread()
    89  }
    90  
    91  func pprofThread() {
    92  	f, err := os.CreateTemp("", "prof")
    93  	if err != nil {
    94  		fmt.Fprintln(os.Stderr, err)
    95  		os.Exit(2)
    96  	}
    97  
    98  	if err := pprof.StartCPUProfile(f); err != nil {
    99  		fmt.Fprintln(os.Stderr, err)
   100  		os.Exit(2)
   101  	}
   102  
   103  	// This goroutine may receive a profiling signal while creating the C-owned
   104  	// thread. If it does, the SetCgoTraceback handler will make the leaf end of
   105  	// the stack look almost (but not exactly) like the stacks the test case is
   106  	// trying to find. Attach a profiler label so the test can filter out those
   107  	// confusing samples.
   108  	pprof.Do(context.Background(), pprof.Labels("ignore", "ignore"), func(ctx context.Context) {
   109  		C.runCPUHogThread()
   110  	})
   111  
   112  	time.Sleep(1 * time.Second)
   113  
   114  	pprof.StopCPUProfile()
   115  
   116  	name := f.Name()
   117  	if err := f.Close(); err != nil {
   118  		fmt.Fprintln(os.Stderr, err)
   119  		os.Exit(2)
   120  	}
   121  
   122  	fmt.Println(name)
   123  }
   124
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