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SubjectRe: Slow, persistent memory leak in 2.6.20
On 8/26/07, Jan Engelhardt <> wrote:
> On Aug 26 2007 11:51, Fred Tyler wrote:
> >On 8/26/07, Fred Tyler <> wrote:
> >> I think I've come across a memory leak in 2.6.20. I've upgraded to the
> >> latest, 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;

(Sorry if this goes to the list twice... Mailer problems.)

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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