Interrupt performance

Slawa Olhovchenkov slw at
Fri Jan 28 17:57:09 UTC 2011

On Fri, Jan 28, 2011 at 07:44:57PM +0200, Stefan Lambrev wrote:

> >> there are profiling tools that you may decide to run.
> > 
> > What tools I can use on amd64?
> Look at this document -
> It contains brief information for all useful profiling tools, or just google for "freebsd kernel profiling"
> I'm not sure what the situation with RealTek driver, but in the past when I have done profiling, I saw that much of
> the CPU time was spent on expensive (for FreeBSD) calls, which where very cheap in linux.

kgmon badly work on amd64.
PmcStat don't supported on this CPU.


This is one of many defects that are not present in high resolution
kernel profiling (kgmon -B instead of kgmon -b; availaible on amd64
and i386).  However, high resolution kernel profiling doesn't work
right with SMP, and was completely broken by gcc-4.  Ordinary
was less completely broken by gcc-4, and you can recover the old
behaviour by turning off new optimizations (mainly -funit-at-a-time
and/or -finline-functions-called-once and or all of -O2).

> > 
> > I boot kernel configured with 'config -p'.
> > Most time in spinlock_exit and acpi_cpu_c1.

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