问题
I am trying to get performance of individual functions within a process. How can I do it using perf tool? Is there any other tool for this?
For example, let's say, main function calls functions A , B , C . I want to get performance of main function as well as functions A,B,C individually .
Is there a good document for understating perf source code?
Thank you.
回答1:
What you want to do is user-land probing. Perf can only do part of it.
Try sudo perf top -p [pid] and then watch the scoreboard. It will show the list of functions sorted by CPU usage. Here is an snapshort of redis during benchmark:
If you want to get more infos of your user-land functions, such as IO usage, latency, memory usage, I strongly suggest you to use Systemtap. It is both scripting language and tool for profiling program on Linux kernel-based operation system. Here is a tutorial about it:
http://qqibrow.github.io/performance-profiling-with-systemtap/
And you don't need to be a expert of systemtap scripting, there are many good script online for you. For example, there is an example about using it to find out the latency of specific function.
https://github.com/openresty/stapxx#func-latency-distr
回答2:
See the Perforator tool, which is built for this: https://github.com/zyedidia/perforator.
Perforator uses the same perf_event_open API that perf uses, but also uses ptrace so that profiling can be selectively enabled only for certain regions of a program (such as functions). See the examples at the Github repository for details.
回答3:
perf is documented at https://perf.wiki.kernel.org/index.php/Main_Page with a tutorial at https://perf.wiki.kernel.org/index.php/Tutorial
perf report gives the breakdown by "command", see https://perf.wiki.kernel.org/index.php/Tutorial#Sample_analysis_with_perf_report. perf annotate provides a way to select what commands to report, see "Source level analysis with perf annotate" in https://perf.wiki.kernel.org/index.php/Tutorial#Options_controlling_output_2.
来源：https://stackoverflow.com/questions/27749804/is-there-a-way-to-find-performance-of-individual-functions-in-a-process-using-pe