Re: kgmon on multiprocessors

On Mon, 2 Jul 2007, Girish Motwani wrote:

>            Does the kernel profiling tool kgmon give accurate information on 
> multiprocessor systems ?  Or is there some other tool for SMP systems ? I 
> tried looking up the archives for information on this, but could not find 
> any.

Girish--

Take a look at hwpmc(4), pmccontrol(8), and pmcstat(8).  These allow you to do 
kernel-only or systemic samplic using performance monitoring counters, 
including looking at CPU time, cache misses, instructions retired, etc.  I 
posted a sixty second howto here:

   http://lists.freebsd.org/pipermail/freebsd-current/2006-February/061096.html

Among other things, you can generate gprof output from PMC; right now, that's 
without full stack traces (and hence callgraphs), but Joseph Koshy has work in 
P4 implementing stack trace support.  I imagine this will go in after the 7.0 
freeze lets up.

Robert N M Watson
Computer Laboratory
University of Cambridge
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