Re: bad rss-counter message in 3.14rc5

[Sasha Levin]

On 03/18/2014 10:12 PM, Hugh Dickins wrote:
> On Tue, 18 Mar 2014, Sasha Levin wrote:
> > On 03/18/2014 08:38 PM, Hugh Dickins wrote:
> > > On Tue, 11 Mar 2014, Dave Jones wrote:
> > > > On Tue, Mar 11, 2014 at 09:36:03PM +0400, Cyrill Gorcunov wrote:
> > > >    > On Tue, Mar 11, 2014 at 01:10:45PM -0400, Dave Jones wrote:
> > > >    > >  >
> > > >    > >  > Dave, iirc trinity can write log file pointing which exactly
> > > > syscall sequence
> > > >    > >  > was passed, right? Share it too please.
> > > >    > >
> > > >    > > Hm, I may have been mistaken, and the damage was done by a previous
> > > > run.
> > > >    > > I went from being able to reproduce it almost instantly to now not
> > > > being able
> > > >    > > to reproduce it at all.  Will keep trying.
> > > >    >
> > > >    > Sasha already gave a link to the syscalls sequence, so no rush.
> > > >
> > > > It'd be nice to get a more concise reproducer, his list had a little of
> > > > everything in there.
> > >
> > > I've so far failed to find any explanation for your swapops.h BUG;
> > > but believe I have identified one cause for "Bad rss-counter"s.
> > >
> > > My hunch is that the swapops.h BUG is "nearby", but I just cannot
> > > fit it together (the swapops.h BUG comes when rmap cannot find all
> > > all the migration entries it inserted earlier: it's a very useful
> > > BUG for validating rmap).
> > >
> > > Untested patch below: I can't quite say Reported-by, because it may
> > > not even be one that you and Sasha have been seeing; but I'm hopeful,
> > > remap_file_pages is in the list.
> > >
> > > Please give this a try, preferably on 3.14-rc or earlier: I've never
> > > seen "Bad rss-counter"s there myself (trinity uses remap_file_pages
> > > a lot more than most of us); but have seen them on mmotm/next, so
> > > some other trigger is coming up there, I'll worry about that once
> > > it reaches 3.15-rc.
> >
> > The patch fixed the "Bad rss-counter" errors I've been seeing both in
> > 3.14-rc7 and -next.
>
> Great, thanks a lot, Sasha.  I was afraid that you'd hit those swapops
> BUGs, which seemed perhaps to be paired with these; but glad to hear
> a positive.  Let's see how Dave fares.  (I've not forgotten shmem
> fallocate, by the way, but those probably aren't as high on my agenda
> as you'd like.)

I do hit the swapops issue a lot, I didn't think that your patch was
supposed to fix that so I didn't mention it.

Thanks for keeping shmem in mind, I've removed shmem from testing for now
but I agree, it's not one of the more important issues to be taken care of.


Thanks,
Sasha

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