(2013/04/09 20:06), Mel Gorman wrote: > Simplistically, the anon and file LRU lists are scanned proportionally > depending on the value of vm.swappiness although there are other factors > taken into account by get_scan_count(). The patch "mm: vmscan: Limit > the number of pages kswapd reclaims" limits the number of pages kswapd > reclaims but it breaks this proportional scanning and may evenly shrink > anon/file LRUs regardless of vm.swappiness. > > This patch preserves the proportional scanning and reclaim. It does mean > that kswapd will reclaim more than requested but the number of pages will > be related to the high watermark. > > [mho...@suse.cz: Correct proportional reclaim for memcg and simplify] > Signed-off-by: Mel Gorman <mgor...@suse.de> > Acked-by: Rik van Riel <r...@redhat.com> > --- > mm/vmscan.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 46 insertions(+), 8 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 4835a7a..0742c45 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1825,13 +1825,21 @@ static void shrink_lruvec(struct lruvec *lruvec, > struct scan_control *sc) > enum lru_list lru; > unsigned long nr_reclaimed = 0; > unsigned long nr_to_reclaim = sc->nr_to_reclaim; > + unsigned long nr_anon_scantarget, nr_file_scantarget; > struct blk_plug plug; > + bool scan_adjusted = false; > > get_scan_count(lruvec, sc, nr); > > + /* Record the original scan target for proportional adjustments later */ > + nr_file_scantarget = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE] + 1; > + nr_anon_scantarget = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON] + 1; > +
I'm sorry I couldn't understand the calc... Assume here nr_file_scantarget = 100 nr_anon_file_target = 100. > blk_start_plug(&plug); > while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || > nr[LRU_INACTIVE_FILE]) { > + unsigned long nr_anon, nr_file, percentage; > + > for_each_evictable_lru(lru) { > if (nr[lru]) { > nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); > @@ -1841,17 +1849,47 @@ static void shrink_lruvec(struct lruvec *lruvec, > struct scan_control *sc) > lruvec, sc); > } > } > + > + if (nr_reclaimed < nr_to_reclaim || scan_adjusted) > + continue; > + > /* > - * On large memory systems, scan >> priority can become > - * really large. This is fine for the starting priority; > - * we want to put equal scanning pressure on each zone. > - * However, if the VM has a harder time of freeing pages, > - * with multiple processes reclaiming pages, the total > - * freeing target can get unreasonably large. > + * For global direct reclaim, reclaim only the number of pages > + * requested. Less care is taken to scan proportionally as it > + * is more important to minimise direct reclaim stall latency > + * than it is to properly age the LRU lists. > */ > - if (nr_reclaimed >= nr_to_reclaim && > - sc->priority < DEF_PRIORITY) > + if (global_reclaim(sc) && !current_is_kswapd()) > break; > + > + /* > + * For kswapd and memcg, reclaim at least the number of pages > + * requested. Ensure that the anon and file LRUs shrink > + * proportionally what was requested by get_scan_count(). We > + * stop reclaiming one LRU and reduce the amount scanning > + * proportional to the original scan target. > + */ > + nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; > + nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; > + Then, nr_file = 80, nr_anon=70. > + if (nr_file > nr_anon) { > + lru = LRU_BASE; > + percentage = nr_anon * 100 / nr_anon_scantarget; > + } else { > + lru = LRU_FILE; > + percentage = nr_file * 100 / nr_file_scantarget; > + } the percentage will be 70. > + > + /* Stop scanning the smaller of the LRU */ > + nr[lru] = 0; > + nr[lru + LRU_ACTIVE] = 0; > + this will stop anon scan. > + /* Reduce scanning of the other LRU proportionally */ > + lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; > + nr[lru] = nr[lru] * percentage / 100;; > + nr[lru + LRU_ACTIVE] = nr[lru + LRU_ACTIVE] * percentage / 100; > + finally, in the next iteration, nr[file] = 80 * 0.7 = 56. After loop, anon-scan is 30 pages , file-scan is 76(20+56) pages.. I think the calc here should be nr[lru] = nr_lru_scantarget * percentage / 100 - nr[lru] Here, 80-70=10 more pages to scan..should be proportional. Am I misunderstanding ? Thanks, -Kame -- 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/