Re: [PATCH] Re: kswapd

[Russell King <rmk@arm.linux.org.uk>]

Kanoj Sarcar writes:
> > Without my patch kswapd uses between 50 and 70% CPU time
> > in a particular workload. Now it uses between 3 and 5%.
> 
> Can you explain how this is happening? I can see that in your patch,
> kswapd does not go thru the loop if need_resched is set, but with
> a single node, 3 zones, I would find it hard to explain such a 
> difference.

kswapd was running until it had a quantum, whether or not it had to
free any more pages.

> > Oh, and the latency problem probably has been fixed too...
> 
> What latency problem? I still believe that the pre3 code is doing
> the right thing, assuming 2.3.43 was doing the right thing.

Check out the linux-kernel archives, specifically for my mails about
NFS/sound problems - it is not good for processes (eg, rpciod) to be
starved of CPU time up to 200-400ms.  It was basically impossible to
play mp3s without the playback basically "stopping" for that period.

(without the patch in, I see kswapd using 200ms-400ms.  With the patch
in, it only uses >10ms very very rarely).
   _____
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  |   |         Russell King        rmk@arm.linux.org.uk      --- ---
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