On Thu, Aug 15, 2013 at 02:56:27PM +0100, Mel Gorman wrote: > On Thu, Aug 15, 2013 at 10:41:39PM +0900, Minchan Kim wrote: > > Hey Mel, > > > > On Thu, Aug 15, 2013 at 11:47:27AM +0100, Mel Gorman wrote: > > > On Thu, Aug 15, 2013 at 06:02:53PM +0800, Hillf Danton wrote: > > > > If the allocation order is not high, direct compaction does nothing. > > > > Can we skip compaction here if order drops to zero? > > > > > > > > > > If the allocation order is not high then > > > > > > pgdat_needs_compaction == (order > 0) == false == no calling compact_pdatt > > > > > > In the case where order is reset to 0 due to fragmentation then it does > > > call compact_pgdat but it does no work due to the cc->order check in > > > __compact_pgdat. > > > > > > > I am looking at mmotm-2013-08-07-16-55 but couldn't find cc->order > > check right before compact_zone in __comact_pgdat. > > Could you pinpoint code piece? > > > > Thanks, I screwed up as that check happens too late. However, it still > ends up not mattering because it does this > > compact_pgdat > -> __compact_pgdat > -> compact_zone > -> compaction_suitable > > For order == 0, compaction_suitable will return either COMPACT_SKIPPED > (if the watermarks are not met) and COMPACT_PARTIAL otherwise. Either > way, compaction doesn't run. In compaction_suitable, it could pass first zone_watermark_ok but failed second zone_watermark_ok while fragindex is -1000 so compaction could run. And we shouldn't depend on such coincidence. > > -- > Mel Gorman > SUSE Labs > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>