Messages in this thread | | | From | "Nick Piggin" <> | Subject | Re: kswapd using all cpu for long periods in 2.4.9-pre4 | Date | Thu, 16 Aug 2001 18:07:16 +1000 |
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Yes you're right, my fault sorry. Leaving it as default does fix the problem. The values were changed using sysctl(8). It writes straight to /proc - my freepages is not readonly for some reason (source has been changed)... anyway, no sysctl(2) backdoors found here.
On related topic - is /Documentation/sysctl/vm.txt up-to-date? Is there a better document to use?
Nick
----- Original Message ----- From: "Linus Torvalds" <torvalds@transmeta.com> Newsgroups: linux.dev.kernel To: <s3293115@student.anu.edu.au>; <linux-kernel@vger.kernel.org>; "Marcelo Tosatti" <marcelo@conectiva.com.br>; "Alan Cox" <alan@lxorguk.ukuu.org.uk> Sent: Thursday, August 16, 2001 3:19 AM Subject: Re: kswapd using all cpu for long periods in 2.4.9-pre4
> I just noticed something.. > > In article <000c01c12569$65581630$0200a8c0@W2K> you write: > > > >kswapd is using all cpu for long periods (100-200 seconds then 100-200 > >seconds break....) there is very little disk activity (heres a vmstat while > >its happening) > > > >mem info during: > >SysRq: Show Memory > >Mem-info: > >Free pages: 3744kB ( 0kB HighMem) > >( Active: 6946, inactive_dirty: 4296, inactive_clean: 895, free: 936 (256 > >512 2048) ) > > This shows your freepages.min low and high: 256. 512 and 2048 > respectively. > > And that's WRONG. Your "freepages.high" is _way_ too high. You must have > changed it through the /proc interface somehow, which should be > impossible (the /proc/sys/vm/freepages file is read-only), but I suspect > that maybe there's a sysctl backdoor. > > How do I know that "freepages.high" is too big? Because it should always > be 3*freepages.min. Yours is 8*min. > > And why does this matter? Because what has apparently happened is: > - your setup somehow modifies the global free target > - but the per-zone targets are still the old ones > > The end result: we always think that we are under a global shortage, but > the actual page freeing routines refuse to free pages because all the > _zones_ think that they are fine. > > Which gives you _exactly_ the behaviour you're describing. "kswapd" will > run forever, and never make any progress at all. > > I wonder if this is more common? Does any of the distributions maybe > have some "system tuning" script that modifies the freepages values > through sysctl? That would certainly explain why some people see the > problem and others do not.. > > How DID you change that value? > > Linus >
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