On Thu 29-10-15 16:17:13, mhocko@xxxxxxxxxx wrote:
[...]
> @@ -3135,13 +3145,56 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> if (gfp_mask & __GFP_NORETRY)
> goto noretry;
>
> - /* Keep reclaiming pages as long as there is reasonable progress */
> + /*
> + * Do not retry high order allocations unless they are __GFP_REPEAT
> + * and even then do not retry endlessly.
> + */
> pages_reclaimed += did_some_progress;
> - if ((did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER) ||
> - ((gfp_mask & __GFP_REPEAT) && pages_reclaimed < (1 << order))) {
> - /* Wait for some write requests to complete then retry */
> - wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC, HZ/50);
> - goto retry;
> + if (order > PAGE_ALLOC_COSTLY_ORDER) {
> + if (!(gfp_mask & __GFP_REPEAT) || pages_reclaimed >= (1<<order))
> + goto noretry;
This is not correct because we could fail __GFP_NOFAIL allocation. It
should do
if (!(gfp_mask & __GFP_NOFAIL) &&
(!(gfp_mask & __GFP_REPEAT) || pages_reclaimed >= (1<<order)))
goto noretry;
It looks rather ugly but it will get much better with patch3 which
reorganizes the code a bit
> +
> + if (did_some_progress)
> + goto retry;
> + }
--
Michal Hocko
SUSE Labs
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