Re: [Qemu-devel] Qemu and heavily increased RSS usage

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Lieven (pl@kamp.de) wrote:
> Am 21.06.2016 um 15:18 schrieb Dr. David Alan Gilbert:
> > * Peter Lieven (pl@kamp.de) wrote:
> > > Hi,
> > > 
> > > while upgrading from Qemu 2.2.0 to Qemu 2.5.1.1 I noticed that the RSS memory usage has heavily increased.
> > > We use hugepages so the RSS memory does not include VM memory. In Qemu 2.2.0 it used to be ~30MB per vServer
> > > and increased to up to 300 - 400MB for Qemu 2.5.1.1 (same with master). The memory increases over time, but seems
> > > not to grow indefinetly. I tried to bisect, but had no result so far that made sense. I also tried valgrind / massif, but
> > > valgrind does not see the allocation (at least at exit) and massif fails to rund due to - so it pretends - heap corruption.
> > > 
> > > Any help or ideas how to debug further would be appreciated.
> > I think I'd try stripping devices off; can you get a similar difference
> > to happen with a guest with no USB, no hugepages, no VGA and a simple
> > locally stored IDE disk?
> > 
> > If you're having trouble bisecting is it possible it's a change
> > in one of the libraries it's linked against?
> > 
> > There was someone asking the other day on #qemu who had a setup that
> > was apparently using much more RAM than expected and we didn't
> > manage to track it down but I can't remember the version being used.
> 
> I currently trying to track the increased usage from release to release. The first increase of RSS usage from ~25MB to ~35MB directly
> after machine setup is introduced by this patch:

OK, while 10MB is bad, I'm more interested in where your other 270MB have gone - hopefully
it's not 27 separate 10MB chunks!

Dave

> 
> commit ba3f4f64b0e941b9e03568b826746941bef071f9
> Author: Paolo Bonzini <pbonzini@redhat.com>
> Date:   Wed Jan 21 12:09:14 2015 +0100
> 
>     exec: RCUify AddressSpaceDispatch
> 
>     Note that even after this patch, most callers of address_space_*
>     functions must still be under the big QEMU lock, otherwise the memory
>     region returned by address_space_translate can disappear as soon as
>     address_space_translate returns.  This will be fixed in the next part
>     of this series.
> 
>     Reviewed-by: Fam Zheng <famz@redhat.com>
>     Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> 
> @Paolo, @Fam, any idea?
> 
> Thanks,
> Peter
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK