Re: Kernel falls apart under light memory pressure (i.e. linkingvmlinux)

[KAMEZAWA Hiroyuki]

On Fri, 20 May 2011 14:36:13 +0900
Minchan Kim <minchan.kim@xxxxxxxxx> wrote:

> On Fri, May 20, 2011 at 2:08 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > On Fri, 20 May 2011 13:20:15 +0900
> > Minchan Kim <minchan.kim@xxxxxxxxx> wrote:
> >
> >> So I want to resolve your problem asap.
> >> We don't have see report about that. Could you do git-bisect?
> >> FYI, Recently, big change of mm is compaction,transparent huge pages.
> >> Kame, could you point out thing related to memcg if you have a mind?
> >>
> >
> > I don't doubt memcg at this stage because it never modify page->flags.
> > Consdering the case, PageActive() is set against off-LRU pages after
> > clear_active_flags() clears it.
> >
> > Hmm, I think I don't understand the lock system fully but...how do you
> > think this ?
> >
> > ==
> >
> > At splitting a hugepage, the routine marks all pmd as "splitting".
> >
> > But assume a racy case where 2 threads run into spit at the
> > same time, one thread wins compound_lock() and do split, another
> > thread should not touch splitted pages.
> 
> Sorry. Now I don't have a time to review in detail.
> When I look it roughly,  page_lock_anon_vma have to prevent it.
> But Andrea needs current this problem and he will catch something we lost. :)
> 
Hmm, maybe I miss something...need to build a test environ on my side.
But I'm not sure I can reproduce it..

Thanks,
-Kame

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