linux-kernel - Re: Slow, persistent memory leak in 2.6.20

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Date:	Sun, 26 Aug 2007 12:14:40 -0400
From:	"Fred Tyler" <fredty8@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Slow, persistent memory leak in 2.6.20

On 8/26/07, Fred Tyler <fredty8@...il.com> wrote:
> On 8/26/07, Jan Engelhardt <jengelh@...putergmbh.de> wrote:
> >
> > On Aug 26 2007 11:51, Fred Tyler wrote:
> > >On 8/26/07, Fred Tyler <fredty8@...il.com> wrote:
> > >> I think I've come across a memory leak in 2.6.20. I've upgraded to the
> > >> latest 2.6.20.17, but it didn't seem to help.
> > >
> > >Sorry to keep replying to my own post, but further investigation
> > >suggests that the memory losses may be occurring at times of heavy
> > >filesystem access. The machines in question run rsyncs of hundreds of
> > >thousands of files every few hours, and I'm starting to think that the
> > >memory loss occurs during these times. I don't know how I'd go about
> > >proving this though...
> >
> > Please rule out filesystem caches by issuing
> >         sync;
> >         echo 3 >/proc/sys/vm/drop_caches;
>
>
> Ok, I did this on a non-production machine that has only been up for a
> few hours, and here's what happened:
>
> ======== Before =========
>
> $ free -m
>              total       used       free     shared    buffers     cached
> Mem:           878        824         54          0        111        422
> -/+ buffers/cache:        290        587
> Swap:           63          0         63
>
>
> ======== After ========
>
> root@b0$ free -m
>              total       used       free     shared    buffers     cached
> Mem:           878         47        830          0          6          4
> -/+ buffers/cache:         36        841
> Swap:           63          0         63
>
> ======================
>
> So, I guess it worked? (I don't know what was supposed to happen, but
> memory usage dropped significantly when I did this.)
>
> However, I'm not sure this staging machine has been up long enough or
> doing enough to exhibit the problem. I can try this on my production
> servers (the ones I provided graphs for) late tonight, but how safe is
> running this command? Does it permanently disable file caching? Do I
> need to reset it afterwards? If I stop all services (databases,
> logging, etc) first, am I protected against data loss?
>
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