On 08/19/2016 04:42 AM, Ralf-Peter Rohbeck wrote:
> On 18.08.2016 13:12, Vlastimil Babka wrote:
>> On 18.8.2016 22:01, Ralf-Peter Rohbeck wrote:
>>> On 17.08.2016 23:57, Vlastimil Babka wrote:
>>>> Vlastimil
>>> Yes, that change was in my test with linux-next-20160817. Here's the diff:
>>>
>>> diff --git a/mm/compaction.c b/mm/compaction.c
>>> index f94ae67..60a9ca2 100644
>>> --- a/mm/compaction.c
>>> +++ b/mm/compaction.c
>>> @@ -1083,8 +1083,10 @@ static void isolate_freepages(struct
>>> compact_control *cc)
>>> continue;
>>>
>>> /* Check the block is suitable for migration */
>>> +/*
>>> if (!suitable_migration_target(page))
>>> continue;
>>> +*/
>> OK, could you please also try if uncommenting the above still works without OOM?
>> Or just plain linux-next-20160817, I guess we don't need the printk's to test
>> this difference.
>>
>> Thanks a lot!
>> Vlastimil
>>
> With the two lines back in I had OOMs again. See the attached logs.
Thanks for the confirmation.
We however shouldn't disable the heuristic completely, so here's a compromise
patch hooking into the new compaction priorities. Can you please test on top of
linux-next?
-----8<-----
>From 0927cc2a4c6a3247111168eace9012c23d06f9db Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@xxxxxxx>
Date: Thu, 18 Aug 2016 16:01:14 +0200
Subject: [PATCH] mm, compaction: make full priority ignore pageblock
suitability
Ralf-Peter Rohbeck has reported premature OOMs for order-2 allocations (stack)
due to OOM rework in 4.7. In his scenario (parallel kernel build and dd writing
to two drives) many pageblocks get marked as Unmovable and compaction free
scanner struggles to isolate free pages. Joonsoo Kim pointed out that the free
scanner skips pageblocks that are not movable to prevent filling them and
forcing non-movable allocations to fallback to other pageblocks. Such heuristic
makes sense to help prevent long-term fragmentation, but premature OOMs are
relatively more urgent problem. As a compromise, this patch disables the
heuristic only for the ultimate compaction priority.
Reported-by: Ralf-Peter Rohbeck <Ralf-Peter.Rohbeck@xxxxxxxxxxx>
Suggested-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
mm/compaction.c | 11 ++++++++---
mm/internal.h | 1 +
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 0bba270f97ad..884b1baa58df 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -997,8 +997,12 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
#ifdef CONFIG_COMPACTION
/* Returns true if the page is within a block suitable for migration to */
-static bool suitable_migration_target(struct page *page)
+static bool suitable_migration_target(struct compact_control *cc,
+ struct page *page)
{
+ if (cc->ignore_block_suitable)
+ return true;
+
/* If the page is a large free page, then disallow migration */
if (PageBuddy(page)) {
/*
@@ -1083,7 +1087,7 @@ static void isolate_freepages(struct compact_control *cc)
continue;
/* Check the block is suitable for migration */
- if (!suitable_migration_target(page))
+ if (!suitable_migration_target(cc, page))
continue;
/* If isolation recently failed, do not retry */
@@ -1656,7 +1660,8 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,
.classzone_idx = classzone_idx,
.direct_compaction = true,
.whole_zone = (prio == COMPACT_PRIO_SYNC_FULL),
- .ignore_skip_hint = (prio == COMPACT_PRIO_SYNC_FULL)
+ .ignore_skip_hint = (prio == COMPACT_PRIO_SYNC_FULL),
+ .ignore_block_suitable = (prio == COMPACT_PRIO_SYNC_FULL)
};
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);
diff --git a/mm/internal.h b/mm/internal.h
index 5214bf8e3171..537ac9951f5f 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -178,6 +178,7 @@ struct compact_control {
unsigned long last_migrated_pfn;/* Not yet flushed page being freed */
enum migrate_mode mode; /* Async or sync migration mode */
bool ignore_skip_hint; /* Scan blocks even if marked skip */
+ bool ignore_block_suitable; /* Scan blocks considered unsuitable */
bool direct_compaction; /* False from kcompactd or /proc/... */
bool whole_zone; /* Whole zone should/has been scanned */
int order; /* order a direct compactor needs */
--
2.9.2
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>