From: Michal Hocko <mhocko@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
David Rientjes <rientjes@google.com>,
Rik van Riel <riel@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 04/11] mm, compaction: don't recheck watermarks after COMPACT_SUCCESS
Date: Thu, 18 Aug 2016 11:03:14 +0200 [thread overview]
Message-ID: <20160818090314.GE30162@dhcp22.suse.cz> (raw)
In-Reply-To: <20160810091226.6709-5-vbabka@suse.cz>
On Wed 10-08-16 11:12:19, Vlastimil Babka wrote:
> Joonsoo has reminded me that in a later patch changing watermark checks
> throughout compaction I forgot to update checks in try_to_compact_pages() and
> compactd_do_work(). Closer inspection however shows that they are redundant now
> that compact_zone() reliably reports success with COMPACT_SUCCESS, as they just
> repeat (a subset) of checks that have just passed. So instead of checking
> watermarks again, just test the return value.
the less watermark checks we do the better because they just increase a
probability of subtle and hard to explain corner cases.
> Also remove the stray "bool success" variable from kcompactd_do_work().
>
> Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/compaction.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index c355bf0d8599..a144f58f7193 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1698,9 +1698,8 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
> alloc_flags, ac_classzone_idx(ac));
> rc = max(status, rc);
>
> - /* If a normal allocation would succeed, stop compacting */
> - if (zone_watermark_ok(zone, order, low_wmark_pages(zone),
> - ac_classzone_idx(ac), alloc_flags)) {
> + /* The allocation should succeed, stop compacting */
> + if (status == COMPACT_SUCCESS) {
> /*
> * We think the allocation will succeed in this zone,
> * but it is not certain, hence the false. The caller
> @@ -1873,8 +1872,6 @@ static void kcompactd_do_work(pg_data_t *pgdat)
> .ignore_skip_hint = true,
>
> };
> - bool success = false;
> -
> trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order,
> cc.classzone_idx);
> count_vm_event(KCOMPACTD_WAKE);
> @@ -1903,9 +1900,7 @@ static void kcompactd_do_work(pg_data_t *pgdat)
> return;
> status = compact_zone(zone, &cc);
>
> - if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone),
> - cc.classzone_idx, 0)) {
> - success = true;
> + if (status == COMPACT_SUCCESS) {
> compaction_defer_reset(zone, cc.order, false);
> } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) {
> /*
> --
> 2.9.2
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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--
Michal Hocko
SUSE Labs
--
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next prev parent reply other threads:[~2016-08-18 9:03 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 [this message]
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
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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