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SubjectRe: [patch] CFS scheduler, -v18

* Willy Tarreau <w@1wt.eu> wrote:

> Today I had a little time to try CFS again (last time it was -v9!). I
> ran it on top of 2.6.20.14, and simply tried ocbench again. You
> remember ? With -v9, I ran 64 processes which all progressed very
> smoothly. With -v18, it's not the case anymore. When I run 64
> processes, only 7 of them show smooth rounds, while all the other ones
> are only updated once a second. Sometimes they only progress by one
> iteration, sometimes by a full round. Some are even updated once ever
> 2 seconds, because if I drag an xterm above them and quickly remove
> it, the xterm leaves a trace there for up to 2 seconds.
>
> Also, only one of my 2 CPUs is used. I see the rq vary between 1 and
> 5, with a permanent 50% idle... :
>
> procs memory swap io system cpu
> r b w swpd free buff cache si so bi bo in cs us sy id
> 1 0 0 0 874400 7864 90436 0 0 0 0 279 2204 50 0 50
> 3 0 0 0 874408 7864 90436 0 0 0 0 273 2122 50 1 50
> 1 0 0 0 874408 7864 90436 0 0 0 0 253 1660 49 1 50
> 3 0 0 0 874408 7864 90436 0 0 0 0 252 1977 50 0 50
> 2 0 0 0 874408 7864 90436 0 0 0 0 253 2274 49 1 50
> 3 0 0 0 874408 7864 90436 0 0 0 0 252 1846 49 1 50
> 1 0 0 0 874408 7864 90436 0 0 0 0 339 1782 49 1 50
>
> I have no idea about what version brought that unexpected behaviour,
> but it's clearly something which needs to be tracked down.

hm, the two problems might be related. Could you try v17 perhaps? In v18
i have 'unified' all the sched.c's between the various kernel releases,
maybe that brought in something unexpected on 2.6.20.14. (perhaps try
v2.6.21.5 based cfs too?)

> My scheduler is at 250 Hz, and here are the values I found in
> /proc/sys/kernel:

could you send me the file the cfs-debug-info.sh script produced. You
can pick the script up from:

http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

(i'd suggest to send it in private mail, output is large and detailed.
If your kernel has no /proc/config.gz then please send me your .config
file too.)

Ingo
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