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 <[email protected]> Signed-off-by: Mel Gorman <[email protected]> --- 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); _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
