Question

如何为perf调用图启用C ++ demangling？当我进入注释模式时，似乎是解码符号，而不是在主调用图中。

示例代码（使用Google Benchmark）：

#include <benchmark/benchmark.h>
#include <vector>

static __attribute__ ((noinline)) int my_really_big_function()
{
  for(size_t i = 0; i < 1000; ++i)
  {
    benchmark::DoNotOptimize(i % 5);
  }
  return 0;
}

static __attribute__ ((noinline)) void caller1()
{
  for(size_t i = 0; i < 1000; ++i)
  {
    benchmark::DoNotOptimize(my_really_big_function());
    benchmark::DoNotOptimize(i % 5);
  }
}

static __attribute__ ((noinline)) void myfun(benchmark::State& state)
{
  while(state.KeepRunning())
  {
    caller1();
  }
}

BENCHMARK(myfun);

BENCHMARK_MAIN();

构建命令：

clang++ main.cpp -o main -fno-omit-frame-pointer -O0 -lpthread -lbenchmark

perf命令：

perf record -g ./main
perf report -g 'graph,0.5,caller'

我也尝试启用--demangle选项，但这似乎不会影响输出。

callgraph缺少解码符号：

Samples: 3K of event 'cycles', Event count (approx.): 2946754102
Children      Self  Command  Shared Object      Symbol
+   99.82%     0.00%  main     main               [.] _ZL5myfunRN9benchmark5StateE
+   99.82%     0.00%  main     main               [.] _ZN9benchmark12_GLOBAL__N_111RunInThreadEPKNS_8internal9Benchmark8InstanceEmiPNS0_11ThreadStatsE
+   99.82%     0.00%  main     main               [.] _ZN9benchmark22RunSpecifiedBenchmarksEPNS_17BenchmarkReporterE
+   99.82%     0.00%  main     main               [.] main
+   99.82%     0.00%  main     libc-2.21.so       [.] __libc_start_main
+   99.82%     0.00%  main     [unknown]          [.] 0x7fbe258d4c544155
+   99.75%     0.30%  main     main               [.] _ZL7caller1v
+   99.52%    99.46%  main     main               [.] _ZL22my_really_big_functionv

带注释的反汇编显示已解除调用的调用：

       │
       │    0000000000404310 <caller1()>:
       │    _ZL7caller1v():
       │      push   %rbp
       │      mov    %rsp,%rbp
       |    $0x30,%rsp
       |   $0x0,-0x18(%rbp)
       │10:   cmpq   $0x3e8,-0x18(%rbp)
       │    ↓ jae    6f
       │    → callq  my_really_big_function()
       │      lea    -0x1c(%rbp),%rcx
       │      mov    %eax,-0x1c(%rbp)
 14.29 │      mov    %rcx,-0x10(%rbp)
       │      mov    -0x10(%rbp),%rcx
       │      lea    -0x28(%rbp),%rcx
       │      mov    $0x5,%eax
       │      mov    %eax,%edx
       │      mov    -0x18(%rbp),%rax
       │      xor    %esi,%esi
       │      mov    %rdx,-0x30(%rbp)
       │      mov    %esi,%edx
       │      mov    -0x30(%rbp),%rdi
       │      div    %rdi
 85.71 │      mov    %rdx,-0x28(%rbp)
       │      mov    %rcx,-0x8(%rbp)
       │      mov    -0x8(%rbp),%rcx
       │      mov    -0x18(%rbp),%rax
       │      add    $0x1,%rax
       │      mov    %rax,-0x18(%rbp)
       │    ↑ jmpq   10
       │6f:   add    $0x30,%rsp
       │      pop    %rbp
       │    ← retq

系统信息：

Ubuntu 15.04 64位
Intel i5-6600k
perf 3.19.8-ckt6
clang 3.6.0-2ubuntu1

Answer 1

我在Ubuntu 15.10上遇到了同样的问题，我在这里找到了解决方案：https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1396654

更新：适用于Ubuntu 18.10

以下是步骤：

sudo apt-get install libiberty-dev binutils-dev
mkdir ~/install
cd ~/install
# If the following apt-get doesn't work on your system,
# uncomment deb-src lines in your /etc/apt/sources.list,
# as suggested by @ctitze
# or you can download it manually from packages.ubuntu.com
# as @aleixrocks suggested in the comment below
apt-get source linux-tools-`uname -r`
sudo apt-get build-dep linux-tools-`uname -r`
cd linux-`uname -r | sed 's/-.*//'`/tools/perf
make

# now you should see the new "perf" executable here
./perf

还应该有一些方法来创建一个新的linux-tools-common软件包，以便将它真正集成到您的系统中。现在要用新的覆盖官方perf，只需设置你的路径：

export PATH=~/install/linux-`uname -r | sed 's/-.*//'`/tools/perf:$PATH

Answer 2

如果您不知道要从packages.ubuntu.com下载什么（如第一个答案），那么您也可以从git下载linux内核源代码：

sudo apt-get install libiberty-dev binutils-dev
mkdir ~/install
cd ~/install
git clone https://github.com/torvalds/linux --depth 1
cd linux/tools/perf
make

# now you should see the new "perf" executable here
./perf

并修改路径（如第一个答案）：

export PATH=~/install/linux/tools/perf:$PATH

perf启用callgraph的demangling

2 个答案: