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  static pthread_t tid;
    21  
    22  void cpuHogThread() {
    23  	int foo = threadSalt1;
    24  	int i;
    25  
    26  	for (i = 0; i < 100000; i++) {
    27  		if (foo > 0) {
    28  			foo *= foo;
    29  		} else {
    30  			foo *= foo + 1;
    31  		}
    32  	}
    33  	threadSalt2 = foo;
    34  }
    35  
    36  void cpuHogThread2() {
    37  }
    38  
    39  struct cgoTracebackArg {
    40  	uintptr_t  context;
    41  	uintptr_t  sigContext;
    42  	uintptr_t* buf;
    43  	uintptr_t  max;
    44  };
    45  
    46  // pprofCgoThreadTraceback is passed to runtime.SetCgoTraceback.
    47  // For testing purposes it pretends that all CPU hits on the cpuHog
    48  // C thread are in cpuHog.
    49  void pprofCgoThreadTraceback(void* parg) {
    50  	struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
    51  	if (pthread_self() == tid) {
    52  		arg->buf[0] = (uintptr_t)(cpuHogThread) + 0x10;
    53  		arg->buf[1] = (uintptr_t)(cpuHogThread2) + 0x4;
    54  		arg->buf[2] = 0;
    55  	} else
    56  		arg->buf[0] = 0;
    57  }
    58  
    59  static void* cpuHogDriver(void* arg __attribute__ ((unused))) {
    60  	while (1) {
    61  		cpuHogThread();
    62  	}
    63  	return 0;
    64  }
    65  
    66  void runCPUHogThread(void) {
    67  	pthread_create(&tid, 0, cpuHogDriver, 0);
    68  }
    69  */
    70  import "C"
    71  
    72  import (
    73  	"context"
    74  	"fmt"
    75  	"os"
    76  	"runtime"
    77  	"runtime/pprof"
    78  	"time"
    79  	"unsafe"
    80  )
    81  
    82  func init() {
    83  	register("CgoPprofThread", CgoPprofThread)
    84  	register("CgoPprofThreadNoTraceback", CgoPprofThreadNoTraceback)
    85  }
    86  
    87  func CgoPprofThread() {
    88  	runtime.SetCgoTraceback(0, unsafe.Pointer(C.pprofCgoThreadTraceback), nil, nil)
    89  	pprofThread()
    90  }
    91  
    92  func CgoPprofThreadNoTraceback() {
    93  	pprofThread()
    94  }
    95  
    96  func pprofThread() {
    97  	f, err := os.CreateTemp("", "prof")
    98  	if err != nil {
    99  		fmt.Fprintln(os.Stderr, err)
   100  		os.Exit(2)
   101  	}
   102  
   103  	if err := pprof.StartCPUProfile(f); err != nil {
   104  		fmt.Fprintln(os.Stderr, err)
   105  		os.Exit(2)
   106  	}
   107  
   108  	// This goroutine may receive a profiling signal while creating the C-owned
   109  	// thread. If it does, the SetCgoTraceback handler will make the leaf end of
   110  	// the stack look almost (but not exactly) like the stacks the test case is
   111  	// trying to find. Attach a profiler label so the test can filter out those
   112  	// confusing samples.
   113  	pprof.Do(context.Background(), pprof.Labels("ignore", "ignore"), func(ctx context.Context) {
   114  		C.runCPUHogThread()
   115  	})
   116  
   117  	time.Sleep(1 * time.Second)
   118  
   119  	pprof.StopCPUProfile()
   120  
   121  	name := f.Name()
   122  	if err := f.Close(); err != nil {
   123  		fmt.Fprintln(os.Stderr, err)
   124  		os.Exit(2)
   125  	}
   126  
   127  	fmt.Println(name)
   128  }
   129
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