From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
David Rientjes <rientjes@google.com>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH v3 13/17] mm, compaction: use correct watermark when checking allocation success
Date: Wed, 6 Jul 2016 14:47:23 +0900 [thread overview]
Message-ID: <20160706054722.GF23627@js1304-P5Q-DELUXE> (raw)
In-Reply-To: <20160624095437.16385-14-vbabka@suse.cz>
On Fri, Jun 24, 2016 at 11:54:33AM +0200, Vlastimil Babka wrote:
> The __compact_finished() function uses low watermark in a check that has to
> pass if the direct compaction is to finish and allocation should succeed. This
> is too pessimistic, as the allocation will typically use min watermark. It may
> happen that during compaction, we drop below the low watermark (due to parallel
> activity), but still form the target high-order page. By checking against low
> watermark, we might needlessly continue compaction.
>
> Similarly, __compaction_suitable() uses low watermark in a check whether
> allocation can succeed without compaction. Again, this is unnecessarily
> pessimistic.
>
> After this patch, these check will use direct compactor's alloc_flags to
> determine the watermark, which is effectively the min watermark.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/compaction.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 76897850c3c2..371760a85085 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1320,7 +1320,7 @@ static enum compact_result __compact_finished(struct zone *zone, struct compact_
> return COMPACT_CONTINUE;
>
> /* Compaction run is not finished if the watermark is not met */
> - watermark = low_wmark_pages(zone);
> + watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK];
finish condition is changed. We have two more watermark checks in
try_to_compact_pages() and kcompactd_do_work() and they should be
changed too.
Thanks.
>
> if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx,
> cc->alloc_flags))
> @@ -1385,7 +1385,7 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
> if (is_via_compact_memory(order))
> return COMPACT_CONTINUE;
>
> - watermark = low_wmark_pages(zone);
> + watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
> /*
> * If watermarks for high-order allocation are already met, there
> * should be no need for compaction at all.
> @@ -1399,7 +1399,7 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
> * This is because during migration, copies of pages need to be
> * allocated and for a short time, the footprint is higher
> */
> - watermark += (2UL << order);
> + watermark = low_wmark_pages(zone) + (2UL << order);
> if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx,
> alloc_flags, wmark_target))
> return COMPACT_SKIPPED;
> --
> 2.8.4
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next prev parent reply other threads:[~2016-07-06 5:44 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-24 9:54 [PATCH v3 00/17] make direct compaction more deterministic Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 01/17] mm, compaction: don't isolate PageWriteback pages in MIGRATE_SYNC_LIGHT mode Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 02/17] mm, page_alloc: set alloc_flags only once in slowpath Vlastimil Babka
2016-06-30 14:44 ` Michal Hocko
2016-06-24 9:54 ` [PATCH v3 03/17] mm, page_alloc: don't retry initial attempt " Vlastimil Babka
2016-06-30 15:03 ` Michal Hocko
2016-06-24 9:54 ` [PATCH v3 04/17] mm, page_alloc: restructure direct compaction handling " Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 05/17] mm, page_alloc: make THP-specific decisions more generic Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 06/17] mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 07/17] mm, compaction: introduce direct compaction priority Vlastimil Babka
2016-06-24 11:39 ` kbuild test robot
2016-06-24 11:51 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 08/17] mm, compaction: simplify contended compaction handling Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 09/17] mm, compaction: make whole_zone flag ignore cached scanner positions Vlastimil Babka
2016-07-06 5:09 ` Joonsoo Kim
2016-07-18 9:12 ` Vlastimil Babka
2016-07-19 6:44 ` Joonsoo Kim
2016-07-19 6:54 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 10/17] mm, compaction: cleanup unused functions Vlastimil Babka
2016-06-24 11:53 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 11/17] mm, compaction: add the ultimate direct compaction priority Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 12/17] mm, compaction: more reliably increase " Vlastimil Babka
2016-07-06 5:39 ` Joonsoo Kim
2016-07-15 13:37 ` Vlastimil Babka
2016-07-18 4:41 ` Joonsoo Kim
2016-07-18 12:21 ` Vlastimil Babka
2016-07-19 4:53 ` Joonsoo Kim
2016-07-19 7:42 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 13/17] mm, compaction: use correct watermark when checking allocation success Vlastimil Babka
2016-07-06 5:47 ` Joonsoo Kim [this message]
2016-07-18 9:23 ` Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 14/17] mm, compaction: create compact_gap wrapper Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 15/17] mm, compaction: use proper alloc_flags in __compaction_suitable() Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 16/17] mm, compaction: require only min watermarks for non-costly orders Vlastimil Babka
2016-06-24 9:54 ` [PATCH v3 17/17] mm, vmscan: make compaction_ready() more accurate and readable Vlastimil Babka
2016-07-06 5:55 ` Joonsoo Kim
2016-07-18 11:48 ` Vlastimil Babka
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