On Mon 23-01-17 11:04:12, Mel Gorman wrote:
[...]
> 1. In should_reclaim_retry, account for SLAB_RECLAIMABLE as available
> pages when deciding to retry reclaim
I am pretty sure I have considered this but then decided to not go that
way. I do not remember details so I will think about this some more. It
might have been just "let's wait for the real issue here". Anyway we can
give it a try and it would be as simple as
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 94ebd30d0f09..87221491be84 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3566,7 +3566,7 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
unsigned long min_wmark = min_wmark_pages(zone);
bool wmark;
- available = reclaimable = zone_reclaimable_pages(zone);
+ available = reclaimable = zone_reclaimable_pages(zone) +
zone_page_state_snapshot(zone, NR_SLAB_RECLAIMABLE);
available -= DIV_ROUND_UP((*no_progress_loops) * available,
MAX_RECLAIM_RETRIES);
available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
I am not sure it would really help much on its own without further
changes to how we scale LRU->slab scanning. Could you give this a try
on top of the mmotm or linux-next tree?
> 2. Stall in should_reclaim_retry for __GFP_NOFAIL|__GFP_NOFS with a
> comment stating that the intent is to allow kswapd make progress
> with the shrinker
The current mmotm tree doesnt need this because we no longer trigger the
oom killer for this combinations of flags.
> 3. Stall __GFP_NOFS in direct reclaimer on a workqueue when it's
> failing to make progress to allow kswapd to do some work. This
> may be impaired if kswapd is locked up waiting for a lock held
> by the direct reclaimer
> 4. Schedule the system workqueue to drain slab for
> __GFP_NOFS|__GFP_NOFAIL.
>
> 3 and 4 are extremely heavy handed so we should try them one at a time.
I am not even sure they are really necessary.
--
Michal Hocko
SUSE Labs
