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-rw-r--r--Documentation/sysctl/vm.txt15
-rw-r--r--include/linux/compaction.h3
-rw-r--r--kernel/sysctl.c15
-rw-r--r--mm/compaction.c12
4 files changed, 44 insertions, 1 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 56dd29b..5fdbb61 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -27,6 +27,7 @@ Currently, these files are in /proc/sys/vm:
- dirty_ratio
- dirty_writeback_centisecs
- drop_caches
+- extfrag_threshold
- hugepages_treat_as_movable
- hugetlb_shm_group
- laptop_mode
@@ -149,6 +150,20 @@ user should run `sync' first.
==============================================================
+extfrag_threshold
+
+This parameter affects whether the kernel will compact memory or direct
+reclaim to satisfy a high-order allocation. /proc/extfrag_index shows what
+the fragmentation index for each order is in each zone in the system. Values
+tending towards 0 imply allocations would fail due to lack of memory,
+values towards 1000 imply failures are due to fragmentation and -1 implies
+that the allocation will succeed as long as watermarks are met.
+
+The kernel will not compact memory in a zone if the
+fragmentation index is <= extfrag_threshold. The default value is 500.
+
+==============================================================
+
hugepages_treat_as_movable
This parameter is only useful when kernelcore= is specified at boot time to
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index eed40ec..3719325 100644
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -15,6 +15,9 @@
extern int sysctl_compact_memory;
extern int sysctl_compaction_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos);
+extern int sysctl_extfrag_threshold;
+extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
extern int fragmentation_index(struct zone *zone, unsigned int order);
extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 284f330..84ff5e7 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -263,6 +263,11 @@ static int min_sched_shares_ratelimit = 100000; /* 100 usec */
static int max_sched_shares_ratelimit = NSEC_PER_SEC; /* 1 second */
#endif
+#ifdef CONFIG_COMPACTION
+static int min_extfrag_threshold;
+static int max_extfrag_threshold = 1000;
+#endif
+
static struct ctl_table kern_table[] = {
{
.procname = "sched_child_runs_first",
@@ -1130,6 +1135,16 @@ static struct ctl_table vm_table[] = {
.mode = 0200,
.proc_handler = sysctl_compaction_handler,
},
+ {
+ .procname = "extfrag_threshold",
+ .data = &sysctl_extfrag_threshold,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = sysctl_extfrag_handler,
+ .extra1 = &min_extfrag_threshold,
+ .extra2 = &max_extfrag_threshold,
+ },
+
#endif /* CONFIG_COMPACTION */
{
.procname = "min_free_kbytes",
diff --git a/mm/compaction.c b/mm/compaction.c
index 9583e19..94cce51 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -433,6 +433,8 @@ static unsigned long compact_zone_order(struct zone *zone,
return compact_zone(zone, &cc);
}
+int sysctl_extfrag_threshold = 500;
+
/**
* try_to_compact_pages - Direct compact to satisfy a high-order allocation
* @zonelist: The zonelist used for the current allocation
@@ -491,7 +493,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
* Only compact if a failure would be due to fragmentation.
*/
fragindex = fragmentation_index(zone, order);
- if (fragindex >= 0 && fragindex <= 500)
+ if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
continue;
if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) {
@@ -572,6 +574,14 @@ int sysctl_compaction_handler(struct ctl_table *table, int write,
return 0;
}
+int sysctl_extfrag_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ proc_dointvec_minmax(table, write, buffer, length, ppos);
+
+ return 0;
+}
+
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
ssize_t sysfs_compact_node(struct sys_device *dev,
struct sysdev_attribute *attr,
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