On Sun, Nov 13, 2011 at 01:37:43AM +0900, Minchan Kim wrote: > I saw the following accouting of compaction during test of the series. s/accouting/accounting/ both here and in the subject. A nicer name the patch would have been "mm: compaction: Only update compact_blocks_moved if compaction was successful" > > compact_blocks_moved 251 > compact_pages_moved 44 > > It's very awkward to me although it's possbile because it means we try to compact 251 blocks > but it just migrated 44 pages. As further investigation, I found isolate_migratepages doesn't > isolate any pages but it returns ISOLATE_SUCCESS and then, it just increases compact_blocks_moved > but doesn't increased compact_pages_moved. > > This patch makes accouting of compaction works only in case of success of isolation. > compact_blocks_moved exists to indicate the rate compaction is scanning pageblocks. If compact_blocks_moved and compact_pages_moved are increasing at a similar rate for example, it could imply that compaction is doing a lot of scanning but is not necessarily useful work. It's not necessarily reflected by compact_fail because that counter is only updated for pages that were isolated from the LRU. I now recognise of course that "compact_blocks_moved" was an *awful* choice of name for this stat. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>