kernel-packages team mailing list archive

[Serge Hallyn <1341195@xxxxxxxxxxxxxxxxxx>]

Quoting Tamas Papp (1341195@xxxxxxxxxxxxxxxxxx):
> On 07/16/2014 09:39 PM, Serge Hallyn wrote
> > I've personally not seen it, and noone on my team, who use a lot of
> > kvm instances, has seen it.  Our two current theories are that (a) it
> > has to do with ksm page migration across numa-nodes, or (b) it has to
> > do with a race with transparent hugepages versus ksm.  For (b) there is
> > already a commit in Linus' tree (f72e7dcd).  For (a), you can probably
> 
> Are you referring to this or a different one?
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1323165

No, this commit is

commit f72e7dcdd25229446b102e587ef2f826f76bff28
Author: Hugh Dickins <hughd@xxxxxxxxxx>
Date:   Mon Jun 23 13:22:05 2014 -0700

    mm: let mm_find_pmd fix buggy race with THP fault

which seems later than that bug.

> > test by setting /sys/kernel/mm/ksm/merge_across_nodes to 0.  (We are
> > trying these as well, but as the testcases are not 100% positive
> > it'd be good to have you try as well)
> 
> It's 1 now.
> Do you you want me to set it now or wait to the result of KSM_ENABLED=0?

Oh - I forgot you had KSM_ENABLED=0 :)  there's no sense changing
merge_across_nodes in the meantime.

(To be sure - /sys/kernel/mm/ksm/run is in fact set to 0 now right?)

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https://bugs.launchpad.net/bugs/1341195

Title:
  KVM guests getting slow by time

Status in “linux” package in Ubuntu:
  Incomplete
Status in “qemu” package in Ubuntu:
  Incomplete

Bug description:
  There is a post with very similar symptoms on serverfault:

  http://serverfault.com/questions/609881/windows-server-2012-on-kvm-on-
  ubuntu-14-04-runs-well-for-a-while-and-then-slows/612084#612084

  
  Basically all kind of KVM guests are getting slow by time, both windows or linux. The more running guests, it happens sooner.
  Switching back to Saucy kernel is a good workaround.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: qemu-kvm 2.0.0+dfsg-2ubuntu1.1
  ProcVersionSignature: Ubuntu 3.13.0-29.53-generic 3.13.11.2
  Uname: Linux 3.13.0-29-generic x86_64
  NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  Date: Sat Jul 12 22:18:49 2014
  SourcePackage: qemu
  UpgradeStatus: No upgrade log present (probably fresh install)

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