Re: [lkp] [mm, page_alloc] d0164adc89: -100.0% fsmark.app_overhead

[Mel Gorman <mgorman@techsingularity.net>]

On Fri, Nov 27, 2015 at 09:14:52AM +0800, Huang, Ying wrote:
> Hi, Mel,
> 
> Mel Gorman <mgorman@techsingularity.net> writes:
> 
> > On Thu, Nov 26, 2015 at 08:56:12AM +0800, kernel test robot wrote:
> >> FYI, we noticed the below changes on
> >> 
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> >> commit d0164adc89f6bb374d304ffcc375c6d2652fe67d ("mm, page_alloc:
> >> distinguish between being unable to sleep, unwilling to sleep and
> >> avoiding waking kswapd")
> >> 
> >> Note: the testing machine is a virtual machine with only 1G memory.
> >> 
> >
> > I'm not actually seeing any problem here. Is this a positive report or
> > am I missing something obvious?
> 
> Sorry the email subject is generated automatically and I forget to
> change it to some meaningful stuff before sending out.  From the testing
> result, we found the commit make the OOM possibility increased from 0%
> to 100% on this machine with small memory.  I also added proc-vmstat
> information data too to help diagnose it.
> 

There is no reference to OOM possibility in the email that I can see. Can
you give examples of the OOM messages that shows the problem sites? It was
suspected that there may be some callers that were accidentally depending
on access to emergency reserves. If so, either they need to be fixed (if
the case is extremely rare) or a small reserve will have to be created
for callers that are not high priority but still cannot reclaim.

Note that I'm travelling a lot over the next two weeks so I'll be slow to
respond but I will get to it.

-- 
Mel Gorman
SUSE Labs