On Wed, Aug 08, 2012 at 01:36:00PM +0900, Minchan Kim wrote: > > > > Second, it updates compact_cached_free_pfn in a more limited set of > > circumstances. > > > > If a scanner has wrapped, it updates compact_cached_free_pfn to the end > > of the zone. Each time a wrapped scanner isoaltes a page, it > > updates compact_cached_free_pfn. The intention is that after > > wrapping, the compact_cached_free_pfn will be at the highest > > pageblock with free pages when compaction completes. > > Okay. > > > > > If a scanner has not wrapped when compaction completes and > > Compaction complete? > Your code seem to do it in isolate_freepages. > Isn't it compaction complete? >
s/compaction/free page isolation/ > > compact_cached_free_pfn is set the end of the the zone, initialise > > it once. > > I can't understad this part. > Could you elaborate a bit more? > Is this better? If a scanner has wrapped, it updates compact_cached_free_pfn to the end of the zone. When a wrapped scanner isolates a page, it updates compact_cached_free_pfn to point to the highest pageblock it can isolate pages from. If a scanner has not wrapped when it has finished isolated pages it checks if compact_cached_free_pfn is pointing to the end of the zone. If so, the value is updated to point to the highest pageblock that pages were isolated from. This value will not be updated again until a free page scanner wraps and resets compact_cached_free_pfn. This is not optimal and it can still race but the compact_cached_free_pfn will be pointing to or very near a pageblock with free pages. -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/