Re: [lkp] [mm, page_alloc] 43993977ba: +88% OOM possibility

From: Michal Hocko
Date: Mon Nov 02 2015 - 05:23:56 EST

On Mon 02-11-15 16:55:15, Huang, Ying wrote:
> Michal Hocko <mhocko@xxxxxxxxxx> writes:
> > It would be interesting to see all the page allocation failure warnings
> > (if they are different). Maybe other callers have relied on GFP_ATOMIC
> > and access to memory reserves. The above path is not this case though.
> I take a look at all dmesgs, and found the backtrace for page allocation
> failure is same for all. Is it possible that this commit cause more
> memory were allocated or kept in memory so that more OOM were triggered?

I can imagine that some of the callers were not converted properly or
missed and a lack of __GFP_KSWAPD_RECLAIM could indeed cause a later
kswapd kick off. I am staring into the commit but nothing has jumped at
me yet. Could you collect /proc/vmstat (snapshot every 1s) on both good
and bad kernels. I expect the later would see a less scanning by kswapd.
Michal Hocko
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