pprof.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  package main
     6  
     7  // Run a slow C function saving a CPU profile.
     8  
     9  /*
    10  #include <stdint.h>
    11  
    12  int salt1;
    13  int salt2;
    14  
    15  void cpuHog() {
    16  	int foo = salt1;
    17  	int i;
    18  
    19  	for (i = 0; i < 100000; i++) {
    20  		if (foo > 0) {
    21  			foo *= foo;
    22  		} else {
    23  			foo *= foo + 1;
    24  		}
    25  	}
    26  	salt2 = foo;
    27  }
    28  
    29  void cpuHog2() {
    30  }
    31  
    32  struct cgoTracebackArg {
    33  	uintptr_t  context;
    34  	uintptr_t  sigContext;
    35  	uintptr_t* buf;
    36  	uintptr_t  max;
    37  };
    38  
    39  // pprofCgoTraceback is passed to runtime.SetCgoTraceback.
    40  // For testing purposes it pretends that all CPU hits in C code are in cpuHog.
    41  // Issue #29034: At least 2 frames are required to verify all frames are captured
    42  // since runtime/pprof ignores the runtime.goexit base frame if it exists.
    43  void pprofCgoTraceback(void* parg) {
    44  	struct cgoTracebackArg* arg = (struct cgoTracebackArg*)(parg);
    45  	arg->buf[0] = (uintptr_t)(cpuHog) + 0x10;
    46  	arg->buf[1] = (uintptr_t)(cpuHog2) + 0x4;
    47  	arg->buf[2] = 0;
    48  }
    49  */
    50  import "C"
    51  
    52  import (
    53  	"fmt"
    54  	"os"
    55  	"runtime"
    56  	"runtime/pprof"
    57  	"time"
    58  	"unsafe"
    59  )
    60  
    61  func init() {
    62  	register("CgoPprof", CgoPprof)
    63  }
    64  
    65  func CgoPprof() {
    66  	runtime.SetCgoTraceback(0, unsafe.Pointer(C.pprofCgoTraceback), nil, nil)
    67  
    68  	f, err := os.CreateTemp("", "prof")
    69  	if err != nil {
    70  		fmt.Fprintln(os.Stderr, err)
    71  		os.Exit(2)
    72  	}
    73  
    74  	if err := pprof.StartCPUProfile(f); err != nil {
    75  		fmt.Fprintln(os.Stderr, err)
    76  		os.Exit(2)
    77  	}
    78  
    79  	t0 := time.Now()
    80  	for time.Since(t0) < time.Second {
    81  		C.cpuHog()
    82  	}
    83  
    84  	pprof.StopCPUProfile()
    85  
    86  	name := f.Name()
    87  	if err := f.Close(); err != nil {
    88  		fmt.Fprintln(os.Stderr, err)
    89  		os.Exit(2)
    90  	}
    91  
    92  	fmt.Println(name)
    93  }
    94
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