Re: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection

[Mel Gorman <mgorman@suse.de>]

> From: Hillf Danton <hdanton@sina.com>
> Subject: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection
> 
> Address the issue of should_continue_reclaim continuing true too often
> for __GFP_RETRY_MAYFAIL attempts when !nr_reclaimed and nr_scanned.
> This could happen during hugetlb page allocation causing stalls for
> minutes or hours.
> 
> We can stop reclaiming pages if compaction reports it can make a progress.
> A code reshuffle is needed to do that. And it has side-effects, however,
> with allocation latencies in other cases but that would come at the cost
> of potential premature reclaim which has consequences of itself.
> 
> We can also bail out of reclaiming pages if we know that there are not
> enough inactive lru pages left to satisfy the costly allocation.
> 
> We can give up reclaiming pages too if we see dryrun occur, with the
> certainty of plenty of inactive pages. IOW with dryrun detected, we are
> sure we have reclaimed as many pages as we could.
> 
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Hillf Danton <hdanton@sina.com>

Acked-by: Mel Gorman <mgorman@suse.de>

Thanks Hillf

-- 
Mel Gorman
SUSE Labs