On Tue 31-05-16 15:08:03, Vlastimil Babka wrote:
[...]
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index da3a62a94b4a..9f83259a18a8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3367,10 +3367,9 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
> bool drained = false;
>
> *did_some_progress = __perform_reclaim(gfp_mask, order, ac);
> - if (unlikely(!(*did_some_progress)))
> - return NULL;
>
> retry:
> + /* We attempt even when no progress, as kswapd might have done some */
> page = get_page_from_freelist(gfp_mask, order, alloc_flags, ac);
Is this really likely to happen, though? Sure we might have last few
reclaimable pages on the LRU lists but I am not sure this would make a
large difference then.
That being said, I do not think this is harmful but I find it a bit
weird to invoke a reclaim and then ignore the feedback... Will leave the
decision up to you but the original patch seemed neater.
>
> /*
> @@ -3378,7 +3377,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
> * pages are pinned on the per-cpu lists or in high alloc reserves.
> * Shrink them them and try again
> */
> - if (!page && !drained) {
> + if (!page && *did_some_progress && !drained) {
> unreserve_highatomic_pageblock(ac);
> drain_all_pages(NULL);
> drained = true;
I do not remember this in the previous version. Why shouldn't we
unreserve highatomic reserves when there was no progress?
--
Michal Hocko
SUSE Labs
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