On Wed, Jul 16, 2014 at 03:48:13PM +0200, Vlastimil Babka wrote: > isolate_migratepages_range() is the main function of the compaction scanner, > called either on a single pageblock by isolate_migratepages() during regular > compaction, or on an arbitrary range by CMA's __alloc_contig_migrate_range(). > It currently perfoms two pageblock-wide compaction suitability checks, and > because of the CMA callpath, it tracks if it crossed a pageblock boundary in > order to repeat those checks. > > However, closer inspection shows that those checks are always true for CMA: > - isolation_suitable() is true because CMA sets cc->ignore_skip_hint to true > - migrate_async_suitable() check is skipped because CMA uses sync compaction > > We can therefore move the compaction-specific checks to isolate_migratepages() > and simplify isolate_migratepages_range(). Furthermore, we can mimic the > freepage scanner family of functions, which has isolate_freepages_block() > function called both by compaction from isolate_freepages() and by CMA from > isolate_freepages_range(), where each use-case adds own specific glue code. > This allows further code simplification. > > Therefore, we rename isolate_migratepages_range() to isolate_freepages_block() > and limit its functionality to a single pageblock (or its subset). For CMA, > a new different isolate_migratepages_range() is created as a CMA-specific > wrapper for the _block() function. The checks specific to compaction are moved > to isolate_migratepages(). As part of the unification of these two families of > functions, we remove the redundant zone parameter where applicable, since zone > pointer is already passed in cc->zone. > > Furthermore, going back to compact_zone() and compact_finished() when pageblock > is found unsuitable (now by isolate_migratepages()) is wasteful - the checks > are meant to skip pageblocks quickly. The patch therefore also introduces a > simple loop into isolate_migratepages() so that it does not return immediately > on failed pageblock checks, but keeps going until isolate_migratepages_range() > gets called once. Similarily to isolate_freepages(), the function periodically > checks if it needs to reschedule or abort async compaction. > > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> > Cc: Minchan Kim <minchan@xxxxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxx> > Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > Cc: Michal Nazarewicz <mina86@xxxxxxxxxx> > Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Cc: Christoph Lameter <cl@xxxxxxxxx> > Cc: Rik van Riel <riel@xxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> -- 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>