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From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
	Joonsoo Kim <js1304@gmail.com>, Rik van Riel <riel@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: [PATCH v2 3/5] mm/compaction: change the timing to check to drop the spinlock
Date: Fri, 14 Feb 2014 15:54:01 +0900	[thread overview]
Message-ID: <1392360843-22261-4-git-send-email-iamjoonsoo.kim@lge.com> (raw)
In-Reply-To: <1392360843-22261-1-git-send-email-iamjoonsoo.kim@lge.com>

It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th pfn
page. This may results in below situation while isolating migratepage.

1. try isolate 0x0 ~ 0x200 pfn pages.
2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop
the spinlock.
3. Then, to complete isolating, retry to aquire the lock.

I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking
the criteria about dropping the lock. This has no harm 0x0 pfn, because,
at this time, locked variable would be false.

Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/mm/compaction.c b/mm/compaction.c
index 0d821a2..b1ba297 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -481,7 +481,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 	cond_resched();
 	for (; low_pfn < end_pfn; low_pfn++) {
 		/* give a chance to irqs before checking need_resched() */
-		if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
+		if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
 			if (should_release_lock(&zone->lru_lock)) {
 				spin_unlock_irqrestore(&zone->lru_lock, flags);
 				locked = false;
-- 
1.7.9.5


WARNING: multiple messages have this Message-ID (diff)
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
	Joonsoo Kim <js1304@gmail.com>, Rik van Riel <riel@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: [PATCH v2 3/5] mm/compaction: change the timing to check to drop the spinlock
Date: Fri, 14 Feb 2014 15:54:01 +0900	[thread overview]
Message-ID: <1392360843-22261-4-git-send-email-iamjoonsoo.kim@lge.com> (raw)
In-Reply-To: <1392360843-22261-1-git-send-email-iamjoonsoo.kim@lge.com>

It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th pfn
page. This may results in below situation while isolating migratepage.

1. try isolate 0x0 ~ 0x200 pfn pages.
2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop
the spinlock.
3. Then, to complete isolating, retry to aquire the lock.

I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking
the criteria about dropping the lock. This has no harm 0x0 pfn, because,
at this time, locked variable would be false.

Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/mm/compaction.c b/mm/compaction.c
index 0d821a2..b1ba297 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -481,7 +481,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
 	cond_resched();
 	for (; low_pfn < end_pfn; low_pfn++) {
 		/* give a chance to irqs before checking need_resched() */
-		if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
+		if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
 			if (should_release_lock(&zone->lru_lock)) {
 				spin_unlock_irqrestore(&zone->lru_lock, flags);
 				locked = false;
-- 
1.7.9.5

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  parent reply	other threads:[~2014-02-14  6:55 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-14  6:53 [PATCH v2 0/5] compaction related commits Joonsoo Kim
2014-02-14  6:53 ` Joonsoo Kim
2014-02-14  6:53 ` [PATCH v2 1/5] mm/compaction: disallow high-order page for migration target Joonsoo Kim
2014-02-14  6:53   ` Joonsoo Kim
2014-02-14  6:54 ` [PATCH v2 2/5] mm/compaction: do not call suitable_migration_target() on every page Joonsoo Kim
2014-02-14  6:54   ` Joonsoo Kim
2014-02-20 16:49   ` Vlastimil Babka
2014-02-20 16:49     ` Vlastimil Babka
2014-02-14  6:54 ` Joonsoo Kim [this message]
2014-02-14  6:54   ` [PATCH v2 3/5] mm/compaction: change the timing to check to drop the spinlock Joonsoo Kim
2014-02-14  6:54 ` [PATCH v2 4/5] mm/compaction: check pageblock suitability once per pageblock Joonsoo Kim
2014-02-14  6:54   ` Joonsoo Kim
2014-02-14  6:54 ` [PATCH v2 5/5] mm/compaction: clean-up code on success of ballon isolation Joonsoo Kim
2014-02-14  6:54   ` Joonsoo Kim
2014-03-03 11:02 ` [PATCH v2 0/5] compaction related commits Vlastimil Babka
2014-03-03 11:02   ` Vlastimil Babka
2014-03-04  0:23   ` Joonsoo Kim
2014-03-04  0:23     ` Joonsoo Kim
2014-03-19  9:38     ` Vlastimil Babka
2014-03-19  9:38       ` Vlastimil Babka

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