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authorCody P Schafer <cody@linux.vnet.ibm.com>2013-07-03 15:01:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-03 16:07:26 -0700
commit4008bab7b3969ad9f9dd1d02096a3f0aa5610bd2 (patch)
treea50e5b26ccc1838fb00f982f3ae9907d978e27fe /mm/page_alloc.c
parent52c2dad914ca3ac84926106d95ddf47de2f40b45 (diff)
downloadop-kernel-dev-4008bab7b3969ad9f9dd1d02096a3f0aa5610bd2.zip
op-kernel-dev-4008bab7b3969ad9f9dd1d02096a3f0aa5610bd2.tar.gz
mm/page_alloc: factor out setting of pcp->high and pcp->batch
"Problems" with the current code: 1: there is a lack of synchronization in setting ->high and ->batch in percpu_pagelist_fraction_sysctl_handler() 2: stop_machine() in zone_pcp_update() is unnecissary. 3: zone_pcp_update() does not consider the case where percpu_pagelist_fraction is non-zero To fix: 1: add memory barriers, a safe ->batch value, an update side mutex when updating ->high and ->batch, and use ACCESS_ONCE() for ->batch users that expect a stable value. 2: avoid draining pages in zone_pcp_update(), rely upon the memory barriers added to fix #1 3: factor out quite a few functions, and then call the appropriate one. Note that it results in a change to the behavior of zone_pcp_update(), which is used by memory_hotplug. I'm rather certain that I've diserned (and preserved) the essential behavior (changing ->high and ->batch), and only eliminated unneeded actions (draining the per cpu pages), but this may not be the case. Further note that the draining of pages that previously took place in zone_pcp_update() occured after repeated draining when attempting to offline a page, and after the offline has "succeeded". It appears that the draining was added to zone_pcp_update() to avoid refactoring setup_pageset() into 2 funtions. This patch: Creates pageset_set_batch() for use in setup_pageset(). pageset_set_batch() imitates the functionality of setup_pagelist_highmark(), but uses the boot time (percpu_pagelist_fraction == 0) calculations for determining ->high based on ->batch. Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com> Cc: Gilad Ben-Yossef <gilad@benyossef.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c3edb62..d4bcc20 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4032,6 +4032,14 @@ static int __meminit zone_batchsize(struct zone *zone)
#endif
}
+/* a companion to setup_pagelist_highmark() */
+static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
+{
+ struct per_cpu_pages *pcp = &p->pcp;
+ pcp->high = 6 * batch;
+ pcp->batch = max(1UL, 1 * batch);
+}
+
static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
{
struct per_cpu_pages *pcp;
@@ -4041,8 +4049,7 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
pcp = &p->pcp;
pcp->count = 0;
- pcp->high = 6 * batch;
- pcp->batch = max(1UL, 1 * batch);
+ pageset_set_batch(p, batch);
for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
INIT_LIST_HEAD(&pcp->lists[migratetype]);
}
@@ -4051,7 +4058,6 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
* setup_pagelist_highmark() sets the high water mark for hot per_cpu_pagelist
* to the value high for the pageset p.
*/
-
static void setup_pagelist_highmark(struct per_cpu_pageset *p,
unsigned long high)
{
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