NKnkurz·Mar 13, 2016
I made a comment directly on the blog post which I'll copy here:
I've also spent a lot of time recently trying to understand how 'perf' works at a low level. I'm getting closer, but a lot of it is still pretty impenetrable. There are four main resources that I'd recommend.
The first, which you've almost surely found, is the "Perf Wiki": https://perf.wiki.kernel.org/index.php/Main_Page
There's not a lot there, but it's a good introduction.
The second, which you might have stumbled across, is the text documentation scattered throughout the kernel source. Most are in https://github.com/torvalds/linux/tree/master/tools/perf/Doc..., but the most useful one is up one directory at https://github.com/torvalds/linux/blob/master/tools/perf/des....
The third is Andi Kleen's PMU Tools: https://github.com/andikleen/pmu-tools
The 'jevents' librar
Read the rest
y within this illustrates how to use 'perf' to set up the counters while using 'rdpmc' from userspace to read them.
The fourth is Vince Weaver's Unofficial Linux Perf Events Web-Page (http://web.eece.maine.edu/~vweaver/projects/perf_events/) and his associated Perf Event Testsuite (https://github.com/deater/perf_event_tests). Tests make wonderful examples.
The deeper I got into it, the more I realized is that 'perf' is still evolving, and there is a lot of anger and discontent below the surface. There were (and are) competing alternatives, but 'perf' is politically in control. Much of what you read about 'perf' should be probably be viewed through the lens of "history written by the victor", and "the vanquished" may have different perspectives.
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Separately, in case anyone is already familiar with the internals, here's an aspect where I'm currently stuck. There is an "offset" field which one is supposed to add to the result read from "rdpmc", but when I do so I get strange problems: https://github.com/nkurz/pmu-tools/commit/f2ab49207d4c7b7ddd...