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[16/16] mm: Account for the number of times direct reclaimers get throttled

Message ID 1342075232-29267-17-git-send-email-mgorman@suse.de
State Not Applicable, archived
Delegated to: David Miller
Headers show

Commit Message

Mel Gorman July 12, 2012, 6:40 a.m. UTC 
Under significant pressure when writing back to network-backed storage,
direct reclaimers may get throttled. This is expected to be a
short-lived event and the processes get woken up again but processes do
get stalled. This patch counts how many times such stalling occurs. It's
up to the administrator whether to reduce these stalls by increasing
min_free_kbytes.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 include/linux/vm_event_item.h |    1 +
 mm/vmscan.c                   |    3 +++
 mm/vmstat.c                   |    1 +
 3 files changed, 5 insertions(+)
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Patch

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 06f8e38..57f7b10 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -30,6 +30,7 @@  enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		FOR_ALL_ZONES(PGSTEAL_DIRECT),
 		FOR_ALL_ZONES(PGSCAN_KSWAPD),
 		FOR_ALL_ZONES(PGSCAN_DIRECT),
+		PGSCAN_DIRECT_THROTTLE,
 #ifdef CONFIG_NUMA
 		PGSCAN_ZONE_RECLAIM_FAILED,
 #endif
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ffe58d3..a75b083 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2177,6 +2177,9 @@  static void throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
 	if (pfmemalloc_watermark_ok(pgdat))
 		return;
 
+	/* Account for the throttling */
+	count_vm_event(PGSCAN_DIRECT_THROTTLE);
+
 	/*
 	 * If the caller cannot enter the filesystem, it's possible that it
 	 * is due to the caller holding an FS lock or performing a journal
diff --git a/mm/vmstat.c b/mm/vmstat.c
index e4db312..dcc3858 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -744,6 +744,7 @@  const char * const vmstat_text[] = {
 	TEXTS_FOR_ZONES("pgsteal_direct")
 	TEXTS_FOR_ZONES("pgscan_kswapd")
 	TEXTS_FOR_ZONES("pgscan_direct")
+	"pgscan_direct_throttle",
 
 #ifdef CONFIG_NUMA
 	"zone_reclaim_failed",