At 2015/1/31 16:31, Vlastimil Babka wrote: > On 01/31/2015 08:49 AM, Zhang Yanfei wrote: >> Hello, >> >> At 2015/1/30 20:34, Joonsoo Kim wrote: >> >> Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> >> >> IMHO, the patch making the free scanner move slower makes both scanners >> meet further. Before this patch, if we isolate too many free pages and even >> after we release the unneeded free pages later the free scanner still already >> be there and will be moved forward again next time -- the free scanner just >> cannot be moved back to grab the free pages we released before no matter where >> the free pages in, pcp or buddy. > > It can be actually moved back. If we are releasing free pages, it means the > current compaction is terminating, and it will set zone->compact_cached_free_pfn > back to the position of the released free page that was furthest back. The next > compaction will start from the cached free pfn. Yeah, you are right. I missed the release_freepages(). Thanks! > > It is however possible that another compaction runs in parallel and has > progressed further and overwrites the cached free pfn. > Hmm, maybe. Thanks. -- 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>