Re: Memory usage with qemu-kvm-0.12.1.1

[Daniel Bareiro <dbareiro@uol.com.ar>]

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Hi, Hugh.

On Wednesday, 30 December 2009 18:14:30 +0000,
Hugh Dickins wrote:

> On Sun, 27 Dec 2009, Rik van Riel wrote:
> > On 12/27/2009 12:12 PM, Avi Kivity wrote:
> > > On 12/27/2009 06:45 PM, Rik van Riel wrote:
> > > > 
> > > > > If so, it doesn't copy stable@kernel.org. Is it queued for -stable?
> > > > 
> > > > I do not believe that it is queued for -stable.
> > > > 
> > > > Do performance fixes fit with -stable policy?
> > > 
> > > If it is a serious regression, I believe it fits.
> > 
> > It's probably been there since 2.6.28, though it might have been
> > introduced later with a cleanup patch.  It seems to go back at
> > least as far as March...
 
> It does look as if it would have got worse in 2.6.31 and 2.6.32
> - though I am reluctant to predict how these scans work out in
> practice from just glancing at the code!
> 
> I agree with Avi (or with Avi's implication), that it would be
> worth sending the fix to -stable - but it would be nice to hear
> if the patch (inline below) actually does fix Daniel's problem.
> It applies and builds correctly on 2.6.31.9 and 2.6.32.3.
> 
> We have certainly sent much more specialized performance fixes
> to -stable (I'm thinking of Lee's anon_vma locking), and I see
> this as more of a straightforward bugfix anyway - people get
> worried by going into swap without understanding why.
> 
> I forget which patch of mine Avi was thinking of,
> but I'm pretty sure Rik's will prove much the more relevant.

I shutdown the virtual machines yesterday and I boot them again and the
swap usage did not exceed the 9 MB / 486 MB with /proc/sys/vm/swappiness
set to 0. Now I tried restarting the host with the same running VM and,
at the moment, the use of swap is zero with /proc/sys/vm/swappiness by
default (60).

root@ubuntu:~# free
             total       used       free     shared    buffers     cached
Mem:       4060340    2299556    1760784          0     837668     133292
-/+ buffers/cache:    1328596    2731744
Swap:       497972          0     497972


What tests would be recommendable to make to reproduce the problem?

You say that the patch applies and builds correctly on 2.6.31.9 and
2.6.32.3. I would like to test it with 2.6.32.3, but I didn't find the
source code of it in [1]. It would have to be in another path?


Thanks for your reply and the patch.

Regards,
Daniel

[1] http://www.kernel.org/pub/linux/kernel/v2.6/
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