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

From: Minchan Kim
Date: Fri May 20 2011 - 00:20:24 EST

On Fri, May 20, 2011 at 12:38 PM, Andrew Lutomirski <luto@xxxxxxx> wrote:
> On Thu, May 19, 2011 at 11:12 PM, KOSAKI Motohiro
> <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>>> Right after that happened, I hit ctrl-c to kill
>>> The system was OK until I typed sync, and then everything hung.
>>> I'm really confused. Âshrink_inactive_list in
>>> RECLAIM_MODE_LUMPYRECLAIM will call one of the isolate_pages functions
>>> with ISOLATE_BOTH. ÂThe resulting list goes into shrink_page_list,
>>> which does VM_BUG_ON(PageActive(page)).
>>> How is that supposed to work?
>> Usually clear_active_flags() clear PG_active before calling
>> shrink_page_list().
>> shrink_inactive_list()
>> Â Âisolate_pages_global()
>> Â Âupdate_isolated_counts()
>> Â Â Â Âclear_active_flags()
>> Â Âshrink_page_list()
> That makes sense. ÂAnd I have CONFIG_COMPACTION=y, so the lumpy mode
> doesn't get set anyway.

Could you see the problem with disabling CONFIG_COMPACTION?

> But the pages I'm seeing have flags=100000000008005D. ÂIf I'm reading
> it right, that means locked,referenced,uptodate,dirty,active. ÂHow
> does a page like that end up in shrink_page_list? ÂI don't see how a
> page that's !PageLRU can get marked Active. ÂNonetheless, I'm hitting
> that VM_BUG_ON.

Thanks for proving that it's not a problem of latest my patch.

> Is there a race somewhere?

First of all, let's finish your first problem about hang. :)
And let's make another thread to fix this problem.

I think this is a severe problem because 2.6.39 includes my deactivate_pages

It touches page states more and more. ( doesn't include it so
it's not a problem of my deactivate_pages problem)
And now inorder-putback series which I will push for 2.6.40 touches it
more and more.

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?

> --Andy

Kind regards,
Minchan Kim
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