Re: [patch] CFS scheduler, -v13

From: Ingo Molnar
Date: Sun May 20 2007 - 02:39:20 EST



* Anant Nitya <kernel@xxxxxxxxxxxxxx> wrote:

> Hi Ingo,
>
> Please ignore my last report about lag problem while using CFS-v13, it
> is working perfectly fine with 2.6.21.1 and the lag I used to see in
> v12 is not there with v13 anymore. [...]

ah, great - i was looking over your debug data and couldnt find the
problem! This moves CFS into the "no open regressions" state again ;-)

> [...] After digging in a bit I found that problem is only occurring in
> 2.6.22-rc1 and it get fired by network usage while transmitting data
> upstream. I don't have any evidence that CFS is involved in lag
> problem since 2.6.22-rc1 with stock scheduler is also having same lag
> problem and it seems directly proportional with upstream speed while
> downstream doesn't shows any misbehavior { at lower upstream speed lag
> is less but with higher upstream speed system starts crawling and
> system load hitting to 70/75}. Lets see how 2.6.22-rc2 is doing.

if that lag still occurs with rc2 then please repeat the following
debugging steps under CFS [which has more instrumentation than the stock
scheduler]:

cat /proc/`pidof firefox-bin`/sched > sched1.txt
echo 0 > /proc/`pidof firefox-bin`/sched

< reproduce the lag in firefox >

cat /proc/`pidof firefox-bin`/sched > sched2.txt

this way we'll be able to tell what nature this delay has. Also, could
you send me your kernel's .config (off-list)?

Ingo
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