Re: mmotm 2011-04-29 - wonky VmRSS and VmHWM values after swapping

From: Andrew Morton
Date: Mon May 02 2011 - 19:45:18 EST


On Mon, 02 May 2011 10:37:22 -0400
Valdis.Kletnieks@xxxxxx wrote:

> On Sun, 01 May 2011 20:26:54 EDT, Valdis.Kletnieks@xxxxxx said:
> > On Fri, 29 Apr 2011 16:26:16 PDT, akpm@xxxxxxxxxxxxxxxxxxxx said:
> > > The mm-of-the-moment snapshot 2011-04-29-16-25 has been uploaded to
> > >
> > > http://userweb.kernel.org/~akpm/mmotm/
> >
> > Dell Latitude E6500 laptop, Core2 Due P8700, 4G RAM, 2G swap.Z86_64 kernel.
> >
> > I was running a backup of the system to an external USB hard drive.
>
> Is a red herring. Am seeing it again, after only 20 minutes of uptime, and so
> far I've only gotten 1.2G or so into the 4G ram (2.5G still free), and never
> touched swap yet.
>
> Aha! I have a reproducer (found while composing this note). /bin/su will
> reliably trigger it (4 tries out of 4, launching from a bash shell that itself
> has sane VmRSS and VmHWM values). So it's a specific code sequence doing it
> (probably one syscall doing something quirky).
>
> Now if I could figure out how to make strace look at the VmRSS after each
> syscall, or get gdb to do similar. Any suggestions? Am open to perf/other
> solutions as well, if anybody has one handy...
>

hm, me too. After boot, hald has a get_mm_counter(mm, MM_ANONPAGES) of
0xffffffffffff3c27. Bisected to Pater's
mm-extended-batches-for-generic-mmu_gather.patch, can't see how it did
that.

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