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mm: vmscan: clean up get_scan_count()
Reclaim pressure balance between anon and file pages is calculated through a tuple of numerators and a shared denominator. Exceptional cases that want to force-scan anon or file pages configure the numerators and denominator such that one list is preferred, which is not necessarily the most obvious way: fraction[0] = 1; fraction[1] = 0; denominator = 1; goto out; Make this easier by making the force-scan cases explicit and use the fractionals only in case they are calculated from reclaim history. [akpm@linux-foundation.org: avoid using unintialized_var()] Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Satoru Moriya <satoru.moriya@hds.com> Cc: Simon Jeons <simon.jeons@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1 changed files with 45 additions and 22 deletions
67
mm/vmscan.c
67
mm/vmscan.c
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@ -1638,6 +1638,13 @@ static int vmscan_swappiness(struct scan_control *sc)
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return mem_cgroup_swappiness(sc->target_mem_cgroup);
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}
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enum scan_balance {
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SCAN_EQUAL,
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SCAN_FRACT,
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SCAN_ANON,
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SCAN_FILE,
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};
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/*
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* Determine how aggressively the anon and file LRU lists should be
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* scanned. The relative value of each set of LRU lists is determined
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@ -1650,14 +1657,16 @@ static int vmscan_swappiness(struct scan_control *sc)
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static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
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unsigned long *nr)
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{
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unsigned long anon, file, free;
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unsigned long anon_prio, file_prio;
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unsigned long ap, fp;
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struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
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u64 fraction[2], denominator;
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enum lru_list lru;
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bool force_scan = false;
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u64 fraction[2];
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u64 denominator = 0; /* gcc */
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struct zone *zone = lruvec_zone(lruvec);
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unsigned long anon_prio, file_prio;
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enum scan_balance scan_balance;
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unsigned long anon, file, free;
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bool force_scan = false;
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unsigned long ap, fp;
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enum lru_list lru;
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/*
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* If the zone or memcg is small, nr[l] can be 0. This
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@ -1676,9 +1685,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
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/* If we have no swap space, do not bother scanning anon pages. */
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if (!sc->may_swap || (nr_swap_pages <= 0)) {
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fraction[0] = 0;
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fraction[1] = 1;
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denominator = 1;
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scan_balance = SCAN_FILE;
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goto out;
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}
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@ -1690,9 +1697,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
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* too expensive.
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*/
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if (!global_reclaim(sc) && !vmscan_swappiness(sc)) {
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fraction[0] = 0;
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fraction[1] = 1;
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denominator = 1;
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scan_balance = SCAN_FILE;
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goto out;
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}
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@ -1702,9 +1707,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
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* (unless the swappiness setting disagrees with swapping).
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*/
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if (!sc->priority && vmscan_swappiness(sc)) {
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fraction[0] = 1;
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fraction[1] = 1;
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denominator = 1;
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scan_balance = SCAN_EQUAL;
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goto out;
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}
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@ -1722,9 +1725,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
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if (global_reclaim(sc)) {
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free = zone_page_state(zone, NR_FREE_PAGES);
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if (unlikely(file + free <= high_wmark_pages(zone))) {
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fraction[0] = 1;
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fraction[1] = 0;
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denominator = 1;
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scan_balance = SCAN_ANON;
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goto out;
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}
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}
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@ -1734,12 +1735,12 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
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* anything from the anonymous working set right now.
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*/
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if (!inactive_file_is_low(lruvec)) {
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fraction[0] = 0;
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fraction[1] = 1;
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denominator = 1;
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scan_balance = SCAN_FILE;
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goto out;
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}
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scan_balance = SCAN_FRACT;
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/*
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* With swappiness at 100, anonymous and file have the same priority.
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* This scanning priority is essentially the inverse of IO cost.
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@ -1792,9 +1793,31 @@ out:
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size = get_lru_size(lruvec, lru);
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scan = size >> sc->priority;
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if (!scan && force_scan)
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scan = min(size, SWAP_CLUSTER_MAX);
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scan = div64_u64(scan * fraction[file], denominator);
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switch (scan_balance) {
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case SCAN_EQUAL:
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/* Scan lists relative to size */
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break;
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case SCAN_FRACT:
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/*
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* Scan types proportional to swappiness and
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* their relative recent reclaim efficiency.
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*/
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scan = div64_u64(scan * fraction[file], denominator);
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break;
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case SCAN_FILE:
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case SCAN_ANON:
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/* Scan one type exclusively */
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if ((scan_balance == SCAN_FILE) != file)
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scan = 0;
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break;
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default:
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/* Look ma, no brain */
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BUG();
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}
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nr[lru] = scan;
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}
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}
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