Messages in this thread | | | Date | Tue, 16 Dec 2008 08:42:40 +1100 | From | Paul Mackerras <> | Subject | Re: [patch] Performance Counters for Linux, v4 |
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Vince Weaver writes:
> I see a large (2300 instruction) fixed overhead when measuring > retired instruction count using the "timec" command > compared to the "pfmon" tool that comes with perfmon3 > (the pfmon tool has essentially no overhead when > doing aggragate counts).
Looks like timec will be counting the fork() and execvp() system calls that are used to run your executable, as well as the executable itself. The fork() overhead could be removed fairly easily I think, the execvp would be hard to get rid of without using ptrace() - and the use of ptrace was one of the things that Ingo et al. objected to in perfmon3.
Paul.
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