This patch adds a proc file /proc/sys/vm/compact_memory. When an arbitrary
value is written to the file, all zones are compacted. The expected user
of such a trigger is a job scheduler that prepares the system before the
target application runs.
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
---
Documentation/sysctl/vm.txt | 11 ++++++++
include/linux/compaction.h | 5 +++
kernel/sysctl.c | 11 ++++++++
mm/compaction.c | 60 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 87 insertions(+), 0 deletions(-)
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index fc5790d..92b5b00 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -19,6 +19,7 @@ files can be found in mm/swap.c.
Currently, these files are in /proc/sys/vm:
- block_dump
+- compact_memory
- dirty_background_bytes
- dirty_background_ratio
- dirty_bytes
@@ -64,6 +65,16 @@ information on block I/O debugging is in Documentation/laptops/laptop-mode.txt.
==============================================================
+compact_memory
+
+Available only when CONFIG_COMPACTION is set. When an arbitrary value
+is written to the file, all zones are compacted such that free memory
+is available in contiguous blocks where possible. This can be important
+for example in the allocation of huge pages although processes will also
+directly compact memory as required.
+
+==============================================================
+
dirty_background_bytes
Contains the amount of dirty memory at which the pdflush background writeback
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 6201371..facaa3d 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -5,4 +5,9 @@
#define COMPACT_INCOMPLETE 0
#define COMPACT_COMPLETE 1
+#ifdef CONFIG_COMPACTION
+extern int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
+#endif /* CONFIG_COMPACTION */
+
#endif /* _LINUX_COMPACTION_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8a68b24..a02c816 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -50,6 +50,7 @@
#include <linux/ftrace.h>
#include <linux/slow-work.h>
#include <linux/perf_event.h>
+#include <linux/compaction.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
@@ -80,6 +81,7 @@ extern int pid_max;
extern int min_free_kbytes;
extern int pid_max_min, pid_max_max;
extern int sysctl_drop_caches;
+extern int sysctl_compact_memory;
extern int percpu_pagelist_fraction;
extern int compat_log;
extern int latencytop_enabled;
@@ -1109,6 +1111,15 @@ static struct ctl_table vm_table[] = {
.mode = 0644,
.proc_handler = drop_caches_sysctl_handler,
},
+#ifdef CONFIG_COMPACTION
+ {
+ .procname = "compact_memory",
+ .data = &sysctl_compact_memory,
+ .maxlen = sizeof(int),
+ .mode = 0200,
+ .proc_handler = sysctl_compaction_handler,
+ },
+#endif /* CONFIG_COMPACTION */
{
.procname = "min_free_kbytes",
.data = &min_free_kbytes,
diff --git a/mm/compaction.c b/mm/compaction.c
index 51ec864..c0b9dc9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -11,6 +11,7 @@
#include <linux/migrate.h>
#include <linux/compaction.h>
#include <linux/mm_inline.h>
+#include <linux/sysctl.h>
#include "internal.h"
/*
@@ -339,3 +340,62 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
return ret;
}
+/* Compact all zones within a node */
+static int compact_node(int nid)
+{
+ int zoneid;
+ pg_data_t *pgdat;
+ struct zone *zone;
+
+ if (nid < 0 || nid > nr_node_ids || !node_online(nid))
+ return -EINVAL;
+ pgdat = NODE_DATA(nid);
+
+ /* Flush pending updates to the LRU lists */
+ lru_add_drain_all();
+
+ for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
+ struct compact_control cc;
+
+ zone = &pgdat->node_zones[zoneid];
+ if (!populated_zone(zone))
+ continue;
+
+ cc.nr_freepages = 0;
+ cc.nr_migratepages = 0;
+ cc.zone = zone;
+ INIT_LIST_HEAD(&cc.freepages);
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ compact_zone(zone, &cc);
+
+ VM_BUG_ON(!list_empty(&cc.freepages));
+ VM_BUG_ON(!list_empty(&cc.migratepages));
+ }
+
+ return 0;
+}
+
+/* Compact all nodes in the system */
+static int compact_nodes(void)
+{
+ int nid;
+
+ for_each_online_node(nid)
+ compact_node(nid);
+
+ return COMPACT_COMPLETE;
+}
+
+/* The written value is actually unused, all memory is compacted */
+int sysctl_compact_memory;
+
+/* This is the entry point for compacting all nodes via /proc/sys/vm */
+int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ if (write)
+ return compact_nodes();
+
+ return 0;
+}
--
1.6.5
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