Re: OOM at low page cache?

[Minchan Kim]

Hello,

On Wed, Jan 28, 2015 at 09:15:50AM -0500, John Moser wrote:
> On 01/28/2015 01:26 AM, Minchan Kim wrote:
> > Hello,
> >
> > On Tue, Jan 27, 2015 at 12:03:34PM +0100, Vlastimil Babka wrote:
> >> CC linux-mm in case somebody has a good answer but missed this in lkml traffic
> >>
> >> On 01/23/2015 11:18 PM, John Moser wrote:
> >>> Why is there no tunable to OOM at low page cache?
> > AFAIR, there were several trial although there wasn't acceptable
> > at that time. One thing I can remember is min_filelist_kbytes.
> > FYI, http://lwn.net/Articles/412313/
> >
> 
> That looks more straight-forward than http://lwn.net/Articles/422291/
> 
> 
> > I'm far away from reclaim code for a long time but when I read again,
> > I found something strange.
> >
> > With having swap in get_scan_count, we keep a mount of file LRU + free
> > as above than high wmark to prevent file LRU thrashing but we don't
> > with no swap. Why?
> >
> 
> That's ... strange.  That means having a token 1MB swap file changes the
> system's practical memory reclaim behavior dramatically?

Basically, yes but 1M is too small. If all of swap consumed, the behavior
will be same so I think we need more explicit logic to prevent cache
thrashing. Could you test below patch?

Thanks.