On Mon, 9 Jun 2014 21:27:16 +0800 Chen Yucong <sla...@gmail.com> wrote:
> Via https://lkml.org/lkml/2013/4/10/334 , we can find that recording the > original scan targets introduces extra 40 bytes on the stack. This patch > is able to avoid this situation and the call to memcpy(). At the same time, > it does not change the relative design idea. > > ratio = original_nr_file / original_nr_anon; > > If (nr_file > nr_anon), then ratio = (nr_file - x) / nr_anon. > x = nr_file - ratio * nr_anon; > > if (nr_file <= nr_anon), then ratio = nr_file / (nr_anon - x). > x = nr_anon - nr_file / ratio; > > ... > Are you sure this is an equivalent-to-before change? If so, then I can't immediately see why :( > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2057,8 +2057,7 @@ out: > static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > { > unsigned long nr[NR_LRU_LISTS]; > - unsigned long targets[NR_LRU_LISTS]; > - unsigned long nr_to_scan; > + unsigned long nr_to_scan, ratio; > enum lru_list lru; > unsigned long nr_reclaimed = 0; > unsigned long nr_to_reclaim = sc->nr_to_reclaim; > @@ -2067,8 +2066,8 @@ static void shrink_lruvec(struct lruvec *lruvec, struct > scan_control *sc) > > get_scan_count(lruvec, sc, nr); > > - /* Record the original scan target for proportional adjustments later */ > - memcpy(targets, nr, sizeof(nr)); > + ratio = (nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE] + 1) / > + (nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON] + 1); > > /* > * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal > @@ -2088,7 +2087,6 @@ static void shrink_lruvec(struct lruvec *lruvec, struct > scan_control *sc) > while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || > nr[LRU_INACTIVE_FILE]) { > unsigned long nr_anon, nr_file, percentage; > - unsigned long nr_scanned; > > for_each_evictable_lru(lru) { > if (nr[lru]) { > @@ -2123,15 +2121,13 @@ static void shrink_lruvec(struct lruvec *lruvec, > struct scan_control *sc) > break; > > if (nr_file > nr_anon) { > - unsigned long scan_target = targets[LRU_INACTIVE_ANON] + > - targets[LRU_ACTIVE_ANON] + 1; > + nr_to_scan = nr_file - ratio * nr_anon; > + percentage = nr[LRU_FILE] * 100 / nr_file; here, nr_file and nr_anon are derived from the contents of nr[]. But nr[] was modified in the for_each_evictable_lru() loop, so its contents now may differ from what was in targets[]? > lru = LRU_BASE; > - percentage = nr_anon * 100 / scan_target; > } else { > - unsigned long scan_target = targets[LRU_INACTIVE_FILE] + > - targets[LRU_ACTIVE_FILE] + 1; > + nr_to_scan = nr_anon - nr_file / ratio; > + percentage = nr[LRU_BASE] * 100 / nr_anon; > lru = LRU_FILE; > - percentage = nr_file * 100 / scan_target; > } > > /* Stop scanning the smaller of the LRU */ > ... -- 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/
