X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=mm%2Fvmscan.c;h=70aa739c6b68beeca628dde8d947023ce4b18ca3;hb=c2eca00fec40a9b3551f0605834acad9336099d1;hp=e7c75a3c6b53fa02c831654a45fad8316f25100d;hpb=fd538803731e50367b7c59ce4ad3454426a3d671;p=karo-tx-linux.git

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e7c75a3c6b53..70aa739c6b68 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -87,6 +87,7 @@ struct scan_control {
 	/* The highest zone to isolate pages for reclaim from */
 	enum zone_type reclaim_idx;
 
+	/* Writepage batching in laptop mode; RECLAIM_WRITE */
 	unsigned int may_writepage:1;
 
 	/* Can mapped pages be reclaimed? */
@@ -1055,6 +1056,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 *    throttling so we could easily OOM just because too many
 		 *    pages are in writeback and there is nothing else to
 		 *    reclaim. Wait for the writeback to complete.
+		 *
+		 * In cases 1) and 2) we activate the pages to get them out of
+		 * the way while we continue scanning for clean pages on the
+		 * inactive list and refilling from the active list. The
+		 * observation here is that waiting for disk writes is more
+		 * expensive than potentially causing reloads down the line.
+		 * Since they're marked for immediate reclaim, they won't put
+		 * memory pressure on the cache working set any longer than it
+		 * takes to write them to disk.
 		 */
 		if (PageWriteback(page)) {
 			/* Case 1 above */
@@ -1062,7 +1072,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			    PageReclaim(page) &&
 			    test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
 				nr_immediate++;
-				goto keep_locked;
+				goto activate_locked;
 
 			/* Case 2 above */
 			} else if (sane_reclaim(sc) ||
@@ -1080,7 +1090,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 				 */
 				SetPageReclaim(page);
 				nr_writeback++;
-				goto keep_locked;
+				goto activate_locked;
 
 			/* Case 3 above */
 			} else {
@@ -1152,13 +1162,18 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
 		if (PageDirty(page)) {
 			/*
-			 * Only kswapd can writeback filesystem pages to
-			 * avoid risk of stack overflow but only writeback
-			 * if many dirty pages have been encountered.
+			 * Only kswapd can writeback filesystem pages
+			 * to avoid risk of stack overflow. But avoid
+			 * injecting inefficient single-page IO into
+			 * flusher writeback as much as possible: only
+			 * write pages when we've encountered many
+			 * dirty pages, and when we've already scanned
+			 * the rest of the LRU for clean pages and see
+			 * the same dirty pages again (PageReclaim).
 			 */
 			if (page_is_file_cache(page) &&
-					(!current_is_kswapd() ||
-					 !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
+			    (!current_is_kswapd() || !PageReclaim(page) ||
+			     !test_bit(PGDAT_DIRTY, &pgdat->flags))) {
 				/*
 				 * Immediately reclaim when written back.
 				 * Similar in principal to deactivate_page()
@@ -1168,7 +1183,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 				inc_node_page_state(page, NR_VMSCAN_IMMEDIATE);
 				SetPageReclaim(page);
 
-				goto keep_locked;
+				goto activate_locked;
 			}
 
 			if (references == PAGEREF_RECLAIM_CLEAN)
@@ -1373,13 +1388,10 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
 	 * wants to isolate pages it will be able to operate on without
 	 * blocking - clean pages for the most part.
 	 *
-	 * ISOLATE_CLEAN means that only clean pages should be isolated. This
-	 * is used by reclaim when it is cannot write to backing storage
-	 *
 	 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
 	 * that it is possible to migrate without blocking
 	 */
-	if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
+	if (mode & ISOLATE_ASYNC_MIGRATE) {
 		/* All the caller can do on PageWriteback is block */
 		if (PageWriteback(page))
 			return ret;
@@ -1387,10 +1399,6 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
 		if (PageDirty(page)) {
 			struct address_space *mapping;
 
-			/* ISOLATE_CLEAN means only clean pages */
-			if (mode & ISOLATE_CLEAN)
-				return ret;
-
 			/*
 			 * Only pages without mappings or that have a
 			 * ->migratepage callback are possible to migrate
@@ -1701,30 +1709,6 @@ static int current_may_throttle(void)
 		bdi_write_congested(current->backing_dev_info);
 }
 
-static bool inactive_reclaimable_pages(struct lruvec *lruvec,
-				struct scan_control *sc, enum lru_list lru)
-{
-	int zid;
-	struct zone *zone;
-	int file = is_file_lru(lru);
-	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
-
-	if (!global_reclaim(sc))
-		return true;
-
-	for (zid = sc->reclaim_idx; zid >= 0; zid--) {
-		zone = &pgdat->node_zones[zid];
-		if (!managed_zone(zone))
-			continue;
-
-		if (zone_page_state_snapshot(zone, NR_ZONE_LRU_BASE +
-				LRU_FILE * file) >= SWAP_CLUSTER_MAX)
-			return true;
-	}
-
-	return false;
-}
-
 /*
  * shrink_inactive_list() is a helper for shrink_node().  It returns the number
  * of reclaimed pages
@@ -1743,9 +1727,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
 	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
 
-	if (!inactive_reclaimable_pages(lruvec, sc, lru))
-		return 0;
-
 	while (unlikely(too_many_isolated(pgdat, file, sc))) {
 		congestion_wait(BLK_RW_ASYNC, HZ/10);
 
@@ -1758,8 +1739,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	if (!sc->may_unmap)
 		isolate_mode |= ISOLATE_UNMAPPED;
-	if (!sc->may_writepage)
-		isolate_mode |= ISOLATE_CLEAN;
 
 	spin_lock_irq(&pgdat->lru_lock);
 
@@ -1833,12 +1812,20 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 		/*
 		 * If dirty pages are scanned that are not queued for IO, it
-		 * implies that flushers are not keeping up. In this case, flag
-		 * the pgdat PGDAT_DIRTY and kswapd will start writing pages from
-		 * reclaim context.
+		 * implies that flushers are not doing their job. This can
+		 * happen when memory pressure pushes dirty pages to the end of
+		 * the LRU before the dirty limits are breached and the dirty
+		 * data has expired. It can also happen when the proportion of
+		 * dirty pages grows not through writes but through memory
+		 * pressure reclaiming all the clean cache. And in some cases,
+		 * the flushers simply cannot keep up with the allocation
+		 * rate. Nudge the flusher threads in case they are asleep, but
+		 * also allow kswapd to start writing pages during reclaim.
 		 */
-		if (stat.nr_unqueued_dirty == nr_taken)
+		if (stat.nr_unqueued_dirty == nr_taken) {
+			wakeup_flusher_threads(0, WB_REASON_VMSCAN);
 			set_bit(PGDAT_DIRTY, &pgdat->flags);
+		}
 
 		/*
 		 * If kswapd scans pages marked marked for immediate
@@ -1956,8 +1943,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
 
 	if (!sc->may_unmap)
 		isolate_mode |= ISOLATE_UNMAPPED;
-	if (!sc->may_writepage)
-		isolate_mode |= ISOLATE_CLEAN;
 
 	spin_lock_irq(&pgdat->lru_lock);
 
@@ -2233,7 +2218,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 	 * system is under heavy pressure.
 	 */
 	if (!inactive_list_is_low(lruvec, true, sc, false) &&
-	    lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES) >> sc->priority) {
+	    lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) {
 		scan_balance = SCAN_FILE;
 		goto out;
 	}
@@ -2300,7 +2285,7 @@ out:
 			unsigned long size;
 			unsigned long scan;
 
-			size = lruvec_lru_size(lruvec, lru, MAX_NR_ZONES);
+			size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
 			scan = size >> sc->priority;
 
 			if (!scan && pass && force_scan)
@@ -2786,8 +2771,6 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
 					  struct scan_control *sc)
 {
 	int initial_priority = sc->priority;
-	unsigned long total_scanned = 0;
-	unsigned long writeback_threshold;
 retry:
 	delayacct_freepages_start();
 
@@ -2800,7 +2783,6 @@ retry:
 		sc->nr_scanned = 0;
 		shrink_zones(zonelist, sc);
 
-		total_scanned += sc->nr_scanned;
 		if (sc->nr_reclaimed >= sc->nr_to_reclaim)
 			break;
 
@@ -2813,20 +2795,6 @@ retry:
 		 */
 		if (sc->priority < DEF_PRIORITY - 2)
 			sc->may_writepage = 1;
-
-		/*
-		 * Try to write back as many pages as we just scanned.  This
-		 * tends to cause slow streaming writers to write data to the
-		 * disk smoothly, at the dirtying rate, which is nice.   But
-		 * that's undesirable in laptop mode, where we *want* lumpy
-		 * writeout.  So in laptop mode, write out the whole world.
-		 */
-		writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
-		if (total_scanned > writeback_threshold) {
-			wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
-						WB_REASON_TRY_TO_FREE_PAGES);
-			sc->may_writepage = 1;
-		}
 	} while (--sc->priority >= 0);
 
 	delayacct_freepages_end();
@@ -3128,6 +3096,7 @@ static bool zone_balanced(struct zone *zone, int order, int classzone_idx)
 	 */
 	clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags);
 	clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags);
+	clear_bit(PGDAT_WRITEBACK, &zone->zone_pgdat->flags);
 
 	return true;
 }