[PATCH 48 of 67] remove lumpy_reclaim

[Andrea Arcangeli <aarcange@redhat.com>]

From: Andrea Arcangeli <aarcange@redhat.com>

Even with memory compaction enabled, without this patch, after:

	echo always >/sys/kernel/mm/transparent_hugepage/defrag

the system becomes unusable and swaps despite gigabytes of clean cache
available in the inactive list. Any frequent high order allocation (despite
being done with noretry/nomemalloc/nowarn) grinds the system to unusable state.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---

diff --git a/mm/vmscan.c b/mm/vmscan.c
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1130,7 +1130,6 @@ static unsigned long shrink_inactive_lis
 	unsigned long nr_scanned = 0;
 	unsigned long nr_reclaimed = 0;
 	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
-	int lumpy_reclaim = 0;
 
 	while (unlikely(too_many_isolated(zone, file, sc))) {
 		congestion_wait(BLK_RW_ASYNC, HZ/10);
@@ -1140,18 +1139,6 @@ static unsigned long shrink_inactive_lis
 			return SWAP_CLUSTER_MAX;
 	}
 
-	/*
-	 * If we need a large contiguous chunk of memory, or have
-	 * trouble getting a small set of contiguous pages, we
-	 * will reclaim both active and inactive pages.
-	 *
-	 * We use the same threshold as pageout congestion_wait below.
-	 */
-	if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
-		lumpy_reclaim = 1;
-	else if (sc->order && priority < DEF_PRIORITY - 2)
-		lumpy_reclaim = 1;
-
 	pagevec_init(&pvec, 1);
 
 	lru_add_drain();
@@ -1163,12 +1150,11 @@ static unsigned long shrink_inactive_lis
 		unsigned long nr_freed;
 		unsigned long nr_active;
 		unsigned int count[NR_LRU_LISTS] = { 0, };
-		int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
 		unsigned long nr_anon;
 		unsigned long nr_file;
 
 		nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX,
-			     &page_list, &nr_scan, sc->order, mode,
+			     &page_list, &nr_scan, sc->order, ISOLATE_INACTIVE,
 				zone, sc->mem_cgroup, 0, file);
 
 		if (scanning_global_lru(sc)) {
@@ -1209,27 +1195,6 @@ static unsigned long shrink_inactive_lis
 		nr_scanned += nr_scan;
 		nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
 
-		/*
-		 * If we are direct reclaiming for contiguous pages and we do
-		 * not reclaim everything in the list, try again and wait
-		 * for IO to complete. This will stall high-order allocations
-		 * but that should be acceptable to the caller
-		 */
-		if (nr_freed < nr_taken && !current_is_kswapd() &&
-		    lumpy_reclaim) {
-			congestion_wait(BLK_RW_ASYNC, HZ/10);
-
-			/*
-			 * The attempt at page out may have made some
-			 * of the pages active, mark them inactive again.
-			 */
-			nr_active = clear_active_flags(&page_list, count);
-			count_vm_events(PGDEACTIVATE, nr_active);
-
-			nr_freed += shrink_page_list(&page_list, sc,
-							PAGEOUT_IO_SYNC);
-		}
-
 		nr_reclaimed += nr_freed;
 
 		local_irq_disable();

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