[Bug 1341195] Re: KVM guests getting slow by time

[Serge Hallyn]

Quoting Tamas Papp (1341195 at bugs.launchpad.net):
> 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 at google.com>
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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Title:
  KVM guests getting slow by time

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