On Thu 19-11-15 15:17:35, David Rientjes wrote:
> On Wed, 18 Nov 2015, Michal Hocko wrote:
[...]
> > @@ -3167,24 +3166,21 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >
> > /*
> > * Do not retry high order allocations unless they are __GFP_REPEAT
> > - * and even then do not retry endlessly unless explicitly told so
> > + * unless explicitly told so.
> > */
> > - pages_reclaimed += did_some_progress;
> > - if (order > PAGE_ALLOC_COSTLY_ORDER) {
> > - if (!(gfp_mask & __GFP_NOFAIL) &&
> > - (!(gfp_mask & __GFP_REPEAT) || pages_reclaimed >= (1<<order)))
> > - goto noretry;
> > -
> > - if (did_some_progress)
> > - goto retry;
> > - }
> > + if (order > PAGE_ALLOC_COSTLY_ORDER &&
> > + !(gfp_mask & (__GFP_REPEAT|__GFP_NOFAIL)))
> > + goto noretry;
>
> Who is allocating order > PAGE_ALLOC_COSTLY_ORDER with __GFP_REPEAT and
> would be affected by this change?
E.g. hugetlb pages. I have tested this in my testing scenario 3.
> >
> > /*
> > * Be optimistic and consider all pages on reclaimable LRUs as usable
> > * but make sure we converge to OOM if we cannot make any progress after
> > * multiple consecutive failed attempts.
> > + * Costly __GFP_REPEAT allocations might have made a progress but this
> > + * doesn't mean their order will become available due to high fragmentation
> > + * so do not reset the backoff for them
> > */
> > - if (did_some_progress)
> > + if (did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER)
> > stall_backoff = 0;
> > else
> > stall_backoff = min(stall_backoff+1, MAX_STALL_BACKOFF);
>
> This makes sense if there are high-order users of __GFP_REPEAT since
> only using a number of pages reclaimed by itself isn't helpful.
Yes, that was my thinking
Thanks!
--
Michal Hocko
SUSE Labs
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