On Wed, Jun 26, 2013 at 12:39:25PM -0700, Andrew Morton wrote: > On Wed, 26 Jun 2013 13:39:23 +0100 Mel Gorman <[email protected]> wrote: > > > Page reclaim at priority 0 will scan the entire LRU as priority 0 is > > considered to be a near OOM condition. Direct reclaim can reach this > > priority while still making reclaim progress. This patch avoids > > reclaiming at priority 0 unless no reclaim progress was made and > > the page allocator would consider firing the OOM killer. The > > user-visible impact is that direct reclaim will not easily reach > > priority 0 and start swapping prematurely. > > That's a bandaid. > > Priority 0 should be a pretty darn rare condition. How often is it > occurring, and do you know why? >
There are no flys on you. The actual rescanning never happens in my experience but priority 0 is reached quickly. Instrumentation showed that it was due to a bug in reclaim/compaction. Please consider replacing the patch with this. ---8<--- mm: vmscan: Do not continue scanning if reclaim was aborted for compaction Direct reclaim is not aborting to allow compaction to go ahead properly. do_try_to_free_pages is told to abort reclaim which is happily ignores and instead increases priority instead until it reaches 0 and starts shrinking file/anon equally. This patch corrects the situation by aborting reclaim when requested instead of raising priority. Signed-off-by: Mel Gorman <[email protected]> --- mm/vmscan.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 2a5dee2..2f0193c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2381,8 +2381,10 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, aborted_reclaim = shrink_zones(zonelist, sc); /* - * Don't shrink slabs when reclaiming memory from - * over limit cgroups + * Don't shrink slabs when reclaiming memory from over limit + * cgroups but do shrink slab at least once when aborting + * reclaim for compaction to avoid unevenly scanning file/anon + * LRU pages over slab pages. */ if (global_reclaim(sc)) { unsigned long lru_pages = 0; @@ -2428,7 +2430,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, WB_REASON_TRY_TO_FREE_PAGES); sc->may_writepage = 1; } - } while (--sc->priority >= 0); + } while (--sc->priority >= 0 && !aborted_reclaim); out: delayacct_freepages_end(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
