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From: Mel Gorman <mel@csn.ul.ie>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
	Christoph Lameter <cl@linux-foundation.org>,
	Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Minchan Kim <minchan.kim@gmail.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 07/14] mm: Export fragmentation index via debugfs
Date: Tue, 20 Apr 2010 22:01:09 +0100	[thread overview]
Message-ID: <1271797276-31358-8-git-send-email-mel@csn.ul.ie> (raw)
In-Reply-To: <1271797276-31358-1-git-send-email-mel@csn.ul.ie>

The fragmentation fragmentation index, is only meaningful if an allocation
would fail and indicates what the failure is due to. A value of -1 such as
in many of the examples above states that the allocation would succeed.
If it would fail, the value is between 0 and 1. A value tending towards
0 implies the allocation failed due to a lack of memory. A value tending
towards 1 implies it failed due to external fragmentation.

For the most part, the huge page size will be the size
of interest but not necessarily so it is exported on a per-order and per-zo
basis via /sys/kernel/debug/extfrag/extfrag_index

> cat /sys/kernel/debug/extfrag/extfrag_index
Node 0, zone      DMA -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.00
Node 0, zone   Normal -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 -1.000 0.954

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
---
 mm/vmstat.c |   84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index d3e0fa1..23a5899 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -16,6 +16,7 @@
 #include <linux/cpu.h>
 #include <linux/vmstat.h>
 #include <linux/sched.h>
+#include <linux/math64.h>
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
 DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
@@ -420,6 +421,33 @@ static void fill_contig_page_info(struct zone *zone,
 						(order - suitable_order);
 	}
 }
+
+/*
+ * A fragmentation index only makes sense if an allocation of a requested
+ * size would fail. If that is true, the fragmentation index indicates
+ * whether external fragmentation or a lack of memory was the problem.
+ * The value can be used to determine if page reclaim or compaction
+ * should be used
+ */
+int fragmentation_index(unsigned int order, struct contig_page_info *info)
+{
+	unsigned long requested = 1UL << order;
+
+	if (!info->free_blocks_total)
+		return 0;
+
+	/* Fragmentation index only makes sense when a request would fail */
+	if (info->free_blocks_suitable)
+		return -1000;
+
+	/*
+	 * Index is between 0 and 1 so return within 3 decimal places
+	 *
+	 * 0 => allocation would fail due to lack of memory
+	 * 1 => allocation would fail due to fragmentation
+	 */
+	return 1000 - div_u64( (1000+(div_u64(info->free_pages * 1000ULL, requested))), info->free_blocks_total);
+}
 #endif
 
 #if defined(CONFIG_PROC_FS) || defined(CONFIG_COMPACTION)
@@ -1087,6 +1115,58 @@ static const struct file_operations unusable_file_ops = {
 	.release	= seq_release,
 };
 
+static void extfrag_show_print(struct seq_file *m,
+					pg_data_t *pgdat, struct zone *zone)
+{
+	unsigned int order;
+	int index;
+
+	/* Alloc on stack as interrupts are disabled for zone walk */
+	struct contig_page_info info;
+
+	seq_printf(m, "Node %d, zone %8s ",
+				pgdat->node_id,
+				zone->name);
+	for (order = 0; order < MAX_ORDER; ++order) {
+		fill_contig_page_info(zone, order, &info);
+		index = fragmentation_index(order, &info);
+		seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
+	}
+
+	seq_putc(m, '\n');
+}
+
+/*
+ * Display fragmentation index for orders that allocations would fail for
+ */
+static int extfrag_show(struct seq_file *m, void *arg)
+{
+	pg_data_t *pgdat = (pg_data_t *)arg;
+
+	walk_zones_in_node(m, pgdat, extfrag_show_print);
+
+	return 0;
+}
+
+static const struct seq_operations extfrag_op = {
+	.start	= frag_start,
+	.next	= frag_next,
+	.stop	= frag_stop,
+	.show	= extfrag_show,
+};
+
+static int extfrag_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &extfrag_op);
+}
+
+static const struct file_operations extfrag_file_ops = {
+	.open		= extfrag_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
 static int __init extfrag_debug_init(void)
 {
 	extfrag_debug_root = debugfs_create_dir("extfrag", NULL);
@@ -1097,6 +1177,10 @@ static int __init extfrag_debug_init(void)
 			extfrag_debug_root, NULL, &unusable_file_ops))
 		return -ENOMEM;
 
+	if (!debugfs_create_file("extfrag_index", 0444,
+			extfrag_debug_root, NULL, &extfrag_file_ops))
+		return -ENOMEM;
+
 	return 0;
 }
 
-- 
1.6.5

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  parent reply	other threads:[~2010-04-20 21:01 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-20 21:01 [PATCH 0/14] Memory Compaction v8 Mel Gorman
2010-04-20 21:01 ` [PATCH 01/14] mm,migration: Take a reference to the anon_vma before migrating Mel Gorman
2010-04-21  2:49   ` KAMEZAWA Hiroyuki
2010-04-20 21:01 ` [PATCH 02/14] mm,migration: Share the anon_vma ref counts between KSM and page migration Mel Gorman
2010-04-20 21:01 ` [PATCH 03/14] mm,migration: Do not try to migrate unmapped anonymous pages Mel Gorman
2010-04-20 21:01 ` [PATCH 04/14] mm,migration: Allow the migration of PageSwapCache pages Mel Gorman
2010-04-21 14:30   ` Christoph Lameter
2010-04-21 15:00     ` Mel Gorman
2010-04-21 15:05       ` Christoph Lameter
2010-04-21 15:14         ` Mel Gorman
2010-04-21 15:31           ` Christoph Lameter
2010-04-21 15:34             ` Mel Gorman
2010-04-21 15:46               ` Christoph Lameter
2010-04-22  9:28                 ` Mel Gorman
2010-04-22  9:46                   ` KAMEZAWA Hiroyuki
2010-04-22 10:13                     ` Minchan Kim
2010-04-22 10:31                       ` KAMEZAWA Hiroyuki
2010-04-22 10:51                         ` KAMEZAWA Hiroyuki
2010-04-22 14:14                           ` Mel Gorman
2010-04-22 14:18                             ` Minchan Kim
2010-04-22 15:40                               ` Mel Gorman
2010-04-22 16:13                                 ` Mel Gorman
2010-04-22 19:29                                 ` Mel Gorman
2010-04-22 19:40                                   ` Christoph Lameter
2010-04-22 23:52                                     ` KAMEZAWA Hiroyuki
2010-04-23  9:03                                       ` Mel Gorman
2010-04-22 14:23                           ` Minchan Kim
2010-04-22 14:40                             ` Minchan Kim
2010-04-22 15:44                               ` Mel Gorman
2010-04-23 18:31                                 ` Andrea Arcangeli
2010-04-23 19:23                                   ` Mel Gorman
2010-04-23 19:39                                     ` Andrea Arcangeli
2010-04-23 21:35                                       ` Andrea Arcangeli
2010-04-24 10:52                                         ` Mel Gorman
2010-04-24 11:13                                           ` Andrea Arcangeli
2010-04-24 11:59                                             ` Mel Gorman
2010-04-24 14:30                                               ` Andrea Arcangeli
2010-04-26 21:54                                               ` Rik van Riel
2010-04-26 22:11                                                 ` Mel Gorman
2010-04-26 22:26                                                   ` Andrea Arcangeli
2010-04-25 14:41                                           ` Andrea Arcangeli
2010-04-27  9:40                                             ` Mel Gorman
2010-04-27 10:41                                               ` KAMEZAWA Hiroyuki
2010-04-27 11:12                                                 ` Mel Gorman
2010-04-27 15:42                                               ` Andrea Arcangeli
2010-04-24 10:50                                       ` Mel Gorman
2010-04-22 15:14                             ` Christoph Lameter
2010-04-23  3:39                               ` Paul E. McKenney
2010-04-23  4:55                               ` Minchan Kim
2010-04-21 23:59     ` KAMEZAWA Hiroyuki
2010-04-22  0:11       ` Minchan Kim
2010-04-20 21:01 ` [PATCH 05/14] mm: Allow CONFIG_MIGRATION to be set without CONFIG_NUMA or memory hot-remove Mel Gorman
2010-04-20 21:01 ` [PATCH 06/14] mm: Export unusable free space index via debugfs Mel Gorman
2010-04-20 21:01 ` Mel Gorman [this message]
2010-04-20 21:01 ` [PATCH 08/14] mm: Move definition for LRU isolation modes to a header Mel Gorman
2010-04-20 21:01 ` [PATCH 09/14] mm,compaction: Memory compaction core Mel Gorman
2010-04-20 21:01 ` [PATCH 10/14] mm,compaction: Add /proc trigger for memory compaction Mel Gorman
2010-04-20 21:01 ` [PATCH 11/14] mm,compaction: Add /sys trigger for per-node " Mel Gorman
2010-04-20 21:01 ` [PATCH 12/14] mm,compaction: Direct compact when a high-order allocation fails Mel Gorman
2010-05-05 12:19   ` [PATCH] fix count_vm_event preempt in memory compaction direct reclaim Andrea Arcangeli
2010-05-05 12:51     ` Mel Gorman
2010-05-05 13:11       ` Andrea Arcangeli
2010-05-05 13:55         ` Mel Gorman
2010-05-05 14:48           ` Andrea Arcangeli
2010-05-05 15:14             ` Mel Gorman
2010-05-05 15:25               ` Andrea Arcangeli
2010-05-05 15:32                 ` Mel Gorman
2010-04-20 21:01 ` [PATCH 13/14] mm,compaction: Add a tunable that decides when memory should be compacted and when it should be reclaimed Mel Gorman
2010-04-20 21:01 ` [PATCH 14/14] mm,compaction: Defer compaction using an exponential backoff when compaction fails Mel Gorman

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