On Fri, Sep 07, 2012 at 12:12:12PM +0800, Shaohua Li wrote:
> Subject: compaction: check migrated page number
>
> isolate_migratepages_range() might isolate none pages, for example, when
> zone->lru_lock is contended and compaction is async. In this case, we should
> abort compaction, otherwise, compact_zone will run a useless loop and make
> zone->lru_lock is even contended.
>
> Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
> ---
> mm/compaction.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: linux/mm/compaction.c
> ===================================================================
> --- linux.orig/mm/compaction.c 2012-09-06 18:37:52.636413761 +0800
> +++ linux/mm/compaction.c 2012-09-07 10:51:16.734081959 +0800
> @@ -618,7 +618,7 @@ typedef enum {
> static isolate_migrate_t isolate_migratepages(struct zone *zone,
> struct compact_control *cc)
> {
> - unsigned long low_pfn, end_pfn;
> + unsigned long low_pfn, end_pfn, old_low_pfn;
>
> /* Do not scan outside zone boundaries */
> low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
> @@ -633,8 +633,9 @@ static isolate_migrate_t isolate_migrate
> }
>
> /* Perform the isolation */
> + old_low_pfn = low_pfn;
> low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
> - if (!low_pfn)
> + if (!low_pfn || old_low_pfn == low_pfn)
> return ISOLATE_ABORT;
>
> cc->migrate_pfn = low_pfn;
Looks good to me.
This other below approach should also work:
diff --git a/mm/compaction.c b/mm/compaction.c
index 7fcd3a5..aefb712 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -70,8 +70,7 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
/* async aborts if taking too long or contended */
if (!cc->sync) {
- if (cc->contended)
- *cc->contended = true;
+ cc->contended = true;
return false;
}
@@ -634,7 +633,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
/* Perform the isolation */
low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
- if (!low_pfn)
+ if (!low_pfn || cc->contended)
return ISOLATE_ABORT;
cc->migrate_pfn = low_pfn;
@@ -831,6 +830,7 @@ static unsigned long compact_zone_order(struct zone *zone,
int order, gfp_t gfp_mask,
bool sync, bool *contended)
{
+ unsigned long ret;
struct compact_control cc = {
.nr_freepages = 0,
.nr_migratepages = 0,
@@ -838,12 +838,14 @@ static unsigned long compact_zone_order(struct zone *zone,
.migratetype = allocflags_to_migratetype(gfp_mask),
.zone = zone,
.sync = sync,
- .contended = contended,
};
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);
- return compact_zone(zone, &cc);
+ ret = compact_zone(zone, &cc);
+ if (contended)
+ *contended = cc.contended;
+ return ret;
}
int sysctl_extfrag_threshold = 500;
diff --git a/mm/internal.h b/mm/internal.h
index 53418cd..dbb32ff 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -130,7 +130,7 @@ struct compact_control {
int order; /* order a direct compactor needs */
int migratetype; /* MOVABLE, RECLAIMABLE etc */
struct zone *zone;
- bool *contended; /* True if a lock was contended */
+ bool contended; /* True if a lock was contended */
};
unsigned long
--
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