On Tue, Jan 18, 2011 at 06:06:52PM +0100, Johannes Weiner wrote: > Up until '3e7d344 mm: vmscan: reclaim order-0 and use compaction > instead of lumpy reclaim', compaction skipped calculating the > fragmentation index of a zone when compaction was explicitely > requested through the procfs knob. > > However, when compaction_suitable was introduced, it did not come with > an extra check for order == -1, set on explicit compaction requests, > and passed this order on to the fragmentation index calculation, where > it overshifts the number of requested pages, leading to a division by > zero. > > This patch makes sure that order == -1 is recognized as the flag it is > rather than passing it along as valid order parameter. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> It could do with a comment saying that order == -1 is expected when compacting via /proc/sys/vm/compact_memory but otherwise; Reviewed-by: Mel Gorman <mel@xxxxxxxxx> > --- > mm/compaction.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 6d592a0..114c145 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -453,6 +453,9 @@ unsigned long compaction_suitable(struct zone *zone, int order) > if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) > return COMPACT_SKIPPED; > > + if (order == -1) > + return COMPACT_CONTINUE; > + > /* > * fragmentation index determines if allocation failures are due to > * low memory or external fragmentation > -- > 1.7.3.4 > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>