From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
David Rientjes <rientjes@google.com>,
Rik van Riel <riel@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders
Date: Tue, 16 Aug 2016 15:16:36 +0900 [thread overview]
Message-ID: <20160816061636.GF17448@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <20160810091226.6709-11-vbabka@suse.cz>
On Wed, Aug 10, 2016 at 11:12:25AM +0200, Vlastimil Babka wrote:
> The __compaction_suitable() function checks the low watermark plus a
> compact_gap() gap to decide if there's enough free memory to perform
> compaction. Then __isolate_free_page uses low watermark check to decide if
> particular free page can be isolated. In the latter case, using low watermark
> is needlessly pessimistic, as the free page isolations are only temporary. For
> __compaction_suitable() the higher watermark makes sense for high-order
> allocations where more freepages increase the chance of success, and we can
> typically fail with some order-0 fallback when the system is struggling to
> reach that watermark. But for low-order allocation, forming the page should not
> be that hard. So using low watermark here might just prevent compaction from
> even trying, and eventually lead to OOM killer even if we are above min
> watermarks.
>
> So after this patch, we use min watermark for non-costly orders in
> __compaction_suitable(), and for all orders in __isolate_free_page().
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/compaction.c | 6 +++++-
> mm/page_alloc.c | 2 +-
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 80eaf9fff114..0bba270f97ad 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1399,10 +1399,14 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
> * isolation. We however do use the direct compactor's classzone_idx to
> * skip over zones where lowmem reserves would prevent allocation even
> * if compaction succeeds.
> + * For costly orders, we require low watermark instead of min for
> + * compaction to proceed to increase its chances.
> * ALLOC_CMA is used, as pages in CMA pageblocks are considered
> * suitable migration targets
> */
> - watermark = low_wmark_pages(zone) + compact_gap(order);
> + watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ?
> + low_wmark_pages(zone) : min_wmark_pages(zone);
> + watermark += compact_gap(order);
> if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
> ALLOC_CMA, wmark_target))
> return COMPACT_SKIPPED;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 621e4211ce16..a5c0f914ec00 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2492,7 +2492,7 @@ int __isolate_free_page(struct page *page, unsigned int order)
>
> if (!is_migrate_isolate(mt)) {
> /* Obey watermarks as if the page was being allocated */
> - watermark = low_wmark_pages(zone) + (1 << order);
> + watermark = min_wmark_pages(zone) + (1UL << order);
This '1 << order' also needs some comment. Why can't we use
compact_gap() in this case?
Thanks.
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next prev parent reply other threads:[~2016-08-16 6:10 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-10 9:12 [PATCH v6 00/11] make direct compaction more deterministic Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 01/11] mm, compaction: make whole_zone flag ignore cached scanner positions Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 02/11] mm, compaction: cleanup unused functions Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 03/11] mm, compaction: rename COMPACT_PARTIAL to COMPACT_SUCCESS Vlastimil Babka
2016-08-18 9:01 ` Michal Hocko
2016-08-10 9:12 ` [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS Vlastimil Babka
2016-08-16 6:12 ` Joonsoo Kim
2016-08-16 6:11 ` Vlastimil Babka
2016-08-18 11:59 ` Vlastimil Babka
2016-08-18 9:03 ` Michal Hocko
2016-08-10 9:12 ` [PATCH v6 05/11] mm, compaction: add the ultimate direct compaction priority Vlastimil Babka
2016-08-16 5:58 ` Joonsoo Kim
2016-08-18 12:23 ` Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 06/11] mm, compaction: more reliably increase " Vlastimil Babka
2016-08-16 6:07 ` Joonsoo Kim
2016-08-16 6:31 ` Vlastimil Babka
2016-08-18 9:10 ` Michal Hocko
2016-08-18 9:44 ` Vlastimil Babka
2016-08-18 9:48 ` Michal Hocko
2016-08-10 9:12 ` [PATCH v6 07/11] mm, compaction: use correct watermark when checking compaction success Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 08/11] mm, compaction: create compact_gap wrapper Vlastimil Babka
2016-08-16 6:15 ` Joonsoo Kim
2016-08-16 6:15 ` Vlastimil Babka
2016-08-16 6:41 ` Joonsoo Kim
2016-08-18 12:13 ` Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 09/11] mm, compaction: use proper alloc_flags in __compaction_suitable() Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 10/11] mm, compaction: require only min watermarks for non-costly orders Vlastimil Babka
2016-08-16 6:16 ` Joonsoo Kim [this message]
2016-08-16 6:36 ` Vlastimil Babka
2016-08-16 6:46 ` Joonsoo Kim
2016-08-18 12:20 ` Vlastimil Babka
2016-08-10 9:12 ` [PATCH v6 11/11] mm, vmscan: make compaction_ready() more accurate and readable Vlastimil Babka
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