On Mon, 30 May 2011 14:13:00 +0100
Mel Gorman <mel@xxxxxxxxx> wrote:
> Asynchronous compaction is used when promoting to huge pages. This is
> all very nice but if there are a number of processes in compacting
> memory, a large number of pages can be isolated. An "asynchronous"
> process can stall for long periods of time as a result with a user
> reporting that firefox can stall for 10s of seconds. This patch aborts
> asynchronous compaction if too many pages are isolated as it's better to
> fail a hugepage promotion than stall a process.
>
> If accepted, this should also be considered for 2.6.39-stable. It should
> also be considered for 2.6.38-stable but ideally [11bc82d6: mm:
> compaction: Use async migration for __GFP_NO_KSWAPD and enforce no
> writeback] would be applied to 2.6.38 before consideration.
>
> Reported-and-Tested-by: Ury Stankevich <urykhy@xxxxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
BTW, I'm surprised to see both of vmscan.c and compaction.c has too_many_isolated()..
in different logic ;)
BTW, compaction ignores UNEVICTABLE LRU ?
Thanks,
-Kame
> ---
> mm/compaction.c | 32 ++++++++++++++++++++++++++------
> 1 files changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 021a296..331a2ee 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -240,11 +240,20 @@ static bool too_many_isolated(struct zone *zone)
> return isolated > (inactive + active) / 2;
> }
>
> +/* possible outcome of isolate_migratepages */
> +typedef enum {
> + ISOLATE_ABORT, /* Abort compaction now */
> + ISOLATE_NONE, /* No pages isolated, continue scanning */
> + ISOLATE_SUCCESS, /* Pages isolated, migrate */
> +} isolate_migrate_t;
> +
> /*
> * Isolate all pages that can be migrated from the block pointed to by
> * the migrate scanner within compact_control.
> + *
> + * Returns false if compaction should abort at this point due to congestion.
> */
> -static unsigned long isolate_migratepages(struct zone *zone,
> +static isolate_migrate_t isolate_migratepages(struct zone *zone,
> struct compact_control *cc)
> {
> unsigned long low_pfn, end_pfn;
> @@ -261,7 +270,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
> /* Do not cross the free scanner or scan within a memory hole */
> if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
> cc->migrate_pfn = end_pfn;
> - return 0;
> + return ISOLATE_NONE;
> }
>
> /*
> @@ -270,10 +279,14 @@ static unsigned long isolate_migratepages(struct zone *zone,
> * delay for some time until fewer pages are isolated
> */
> while (unlikely(too_many_isolated(zone))) {
> + /* async migration should just abort */
> + if (!cc->sync)
> + return ISOLATE_ABORT;
> +
> congestion_wait(BLK_RW_ASYNC, HZ/10);
>
> if (fatal_signal_pending(current))
> - return 0;
> + return ISOLATE_ABORT;
> }
>
> /* Time to isolate some pages for migration */
> @@ -358,7 +371,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
>
> trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
>
> - return cc->nr_migratepages;
> + return ISOLATE_SUCCESS;
> }
>
> /*
> @@ -522,9 +535,15 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
> unsigned long nr_migrate, nr_remaining;
> int err;
>
> - if (!isolate_migratepages(zone, cc))
> + switch (isolate_migratepages(zone, cc)) {
> + case ISOLATE_ABORT:
> + goto out;
> + case ISOLATE_NONE:
> continue;
> -
> + case ISOLATE_SUCCESS:
> + ;
> + }
> +
> nr_migrate = cc->nr_migratepages;
> err = migrate_pages(&cc->migratepages, compaction_alloc,
> (unsigned long)cc, false,
> @@ -547,6 +566,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
>
> }
>
> +out:
> /* Release free pages and check accounting */
> cc->nr_freepages -= release_freepages(&cc->freepages);
> VM_BUG_ON(cc->nr_freepages != 0);
>
> --
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