可以“记录"或“性能记录"样本子进程? [英] can "perf record" or "perf-record" sample child processes?

问题描述

假设我有一个线束二进制文件，可以根据命令行选项生成不同的基准.我对抽样这些基准非常感兴趣.

我有3种选择:

1. 更改工具二进制文件以生成性能记录"子进程，该子进程运行基准并进行采样

2. 只需执行"perf record $ harness-binary"，希望它也会对子进程进行采样.

3. 性能记录-a $ harness-binary"，它将执行从所有CPU进行系统范围的收集".这需要root访问，因此在我的情况下不可行.

如果性能记录确实对子进程进行采样，则方法2是干净的.有人可以帮助确认是否是这种情况吗?高度赞赏指向文档或性能代码的指针.

如果方法2是可行的，并且基准测试比测试工具要消耗更多的CPU资源，我认为基准采样的质量应该相当不错，对吧?

谢谢

解决方案

perf记录(不带 -a 选项)记录所有从目标进程分叉(和克隆的线程)的进程开始记录后.使用 perf record ./program ，它也会配置所有子进程，而使用 perf record -p $ PID ，并附加到已经运行的$ PID上，它将配置目标进程和所有附加后启动子进程.默认情况下，分析继承处于启用状态(所需代码如下: attr-> inherit =！opts-> no_inherit; & https://perf.wiki.kernel.org/index.php/Tutorial

计数和继承

默认情况下，该进程的所有线程以及后续子进程和线程的perf stat计数.可以使用-i选项更改.无法获得每个线程或每个进程的计数细分.

还有 -i 选项也用于 perf记录:

just do "perf record $harness-binary" hoping it will sample the child process too.

"perf record -a $harness-binary" which would do a "System-wide collection from all CPUs.". This requires root access, therefore not feasible in my case.

Approach #2 is clean if perf-record really samples the child process. Can somebody help to confirm if this is the case? Pointers to documents or perf code would be highly appreciated.

If approach #2 is feasible and the benchmarks is much more CPU-intensive than the harness, I think the quality of the benchmark sampling should be reasonably good, right?

Thanks

解决方案

perf record without -a option record all processes, forked (and threads cloned) from target process after starting of record. With perf record ./program it will profile all child processes too, and with perf record -p $PID with attaching to already running $PID it will profile target process and all child processes started after attaching. Profiling inheritance is enabled by default (code as required: attr->inherit = !opts->no_inherit; & no_inherit) and can be disabled with -i option and also disabled by -t and --per-thread.

This inheritance is like in perf stat: https://perf.wiki.kernel.org/index.php/Tutorial

Counting and inheritance

By default, perf stat counts for all threads of the process and subsequent child processes and threads. This can be altered using the -i option. It is not possible to obtain a count breakdown per-thread or per-process.

And -i option is there for perf record too: http://man7.org/linux/man-pages/man1/perf-record.1.html

  -i, --no-inherit
      Child tasks do not inherit counters.

perf report can filter events from some PID from collected combined perf.data file.

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