diff options
| -rw-r--r-- | mm/vmscan.c | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 1f35364e0feb..b3829c7e3a7d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3123,7 +3123,6 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) .may_writepage = !laptop_mode, .may_unmap = 1, .may_swap = 1, - .reclaim_idx = classzone_idx, }; count_vm_event(PAGEOUTRUN); @@ -3131,12 +3130,17 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) bool raise_priority = true; sc.nr_reclaimed = 0; + sc.reclaim_idx = classzone_idx; /* - * If the number of buffer_heads in the machine exceeds the - * maximum allowed level then reclaim from all zones. This is - * not specific to highmem as highmem may not exist but it is - * it is expected that buffer_heads are stripped in writeback. + * If the number of buffer_heads exceeds the maximum allowed + * then consider reclaiming from all zones. This has a dual + * purpose -- on 64-bit systems it is expected that + * buffer_heads are stripped during active rotation. On 32-bit + * systems, highmem pages can pin lowmem memory and shrinking + * buffers can relieve lowmem pressure. Reclaim may still not + * go ahead if all eligible zones for the original allocation + * request are balanced to avoid excessive reclaim from kswapd. */ if (buffer_heads_over_limit) { for (i = MAX_NR_ZONES - 1; i >= 0; i--) { @@ -3155,14 +3159,16 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) * Scanning from low to high zone would allow congestion to be * cleared during a very small window when a small low * zone was balanced even under extreme pressure when the - * overall node may be congested. + * overall node may be congested. Note that sc.reclaim_idx + * is not used as buffer_heads_over_limit may have adjusted + * it. */ - for (i = sc.reclaim_idx; i >= 0; i--) { + for (i = classzone_idx; i >= 0; i--) { zone = pgdat->node_zones + i; if (!populated_zone(zone)) continue; - if (zone_balanced(zone, sc.order, sc.reclaim_idx)) + if (zone_balanced(zone, sc.order, classzone_idx)) goto out; } |