Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q5

Ingo Molnar
2004-08-31T07:05:31Z

* Lee Revell <rlrevell@joe-job.com> wrote:

> Otherwise, this looks pretty good. Here is a new one, I got this
> starting X:
>
> http://krustophenia.net/testresults.php?dataset=2.6.9-rc1-bk4-Q5#/var/www/2.6.9-rc1-bk4-Q5/trace2.txt

ok, MTRR setting overhead. It is not quite clear to me which precise
code took so much time, could you stick a couple of 'mcount();' lines
into arch/i386/kernel/cpu/mtrr/generic.c's prepare_set() and
generic_set_mtrr() functions? In particular the wbinvd() [cache
invalidation] instructions within prepare_set() look like a possible
source of latency.

(explicit calls to mcount() can be used to break up latency paths
manually - they wont affect the latency itself, they make the resulting
trace more finegrained.)

Ingo