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-rw-r--r--Documentation/sysctl/vm.txt18
-rw-r--r--include/linux/mm.h1
-rw-r--r--include/linux/mmzone.h2
-rw-r--r--kernel/sysctl.c10
-rw-r--r--mm/page_alloc.c29
5 files changed, 58 insertions, 2 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 89a887c76629..cb0368459da3 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -803,6 +803,24 @@ performance impact. Reclaim code needs to take various locks to find freeable
directory and inode objects. With vfs_cache_pressure=1000, it will look for
ten times more freeable objects than there are.
+=============================================================
+
+watermark_scale_factor:
+
+This factor controls the aggressiveness of kswapd. It defines the
+amount of memory left in a node/system before kswapd is woken up and
+how much memory needs to be free before kswapd goes back to sleep.
+
+The unit is in fractions of 10,000. The default value of 10 means the
+distances between watermarks are 0.1% of the available memory in the
+node/system. The maximum value is 1000, or 10% of memory.
+
+A high rate of threads entering direct reclaim (allocstall) or kswapd
+going to sleep prematurely (kswapd_low_wmark_hit_quickly) can indicate
+that the number of free pages kswapd maintains for latency reasons is
+too small for the allocation bursts occurring in the system. This knob
+can then be used to tune kswapd aggressiveness accordingly.
+
==============================================================
zone_reclaim_mode:
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 75d1907b9009..f7fd64227d3a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1889,6 +1889,7 @@ extern void zone_pcp_reset(struct zone *zone);
/* page_alloc.c */
extern int min_free_kbytes;
+extern int watermark_scale_factor;
/* nommu.c */
extern atomic_long_t mmap_pages_allocated;
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index bdd9a270a813..c60df9257cc7 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -841,6 +841,8 @@ static inline int is_highmem(struct zone *zone)
struct ctl_table;
int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
+int watermark_scale_factor_sysctl_handler(struct ctl_table *, int,
+ void __user *, size_t *, loff_t *);
extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f5102fabef7f..725587f10667 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -126,6 +126,7 @@ static int __maybe_unused two = 2;
static int __maybe_unused four = 4;
static unsigned long one_ul = 1;
static int one_hundred = 100;
+static int one_thousand = 1000;
#ifdef CONFIG_PRINTK
static int ten_thousand = 10000;
#endif
@@ -1404,6 +1405,15 @@ static struct ctl_table vm_table[] = {
.extra1 = &zero,
},
{
+ .procname = "watermark_scale_factor",
+ .data = &watermark_scale_factor,
+ .maxlen = sizeof(watermark_scale_factor),
+ .mode = 0644,
+ .proc_handler = watermark_scale_factor_sysctl_handler,
+ .extra1 = &one,
+ .extra2 = &one_thousand,
+ },
+ {
.procname = "percpu_pagelist_fraction",
.data = &percpu_pagelist_fraction,
.maxlen = sizeof(percpu_pagelist_fraction),
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 941b802e11ec..d156310aedeb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -249,6 +249,7 @@ compound_page_dtor * const compound_page_dtors[] = {
int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;
+int watermark_scale_factor = 10;
static unsigned long __meminitdata nr_kernel_pages;
static unsigned long __meminitdata nr_all_pages;
@@ -6347,8 +6348,17 @@ static void __setup_per_zone_wmarks(void)
zone->watermark[WMARK_MIN] = tmp;
}
- zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + (tmp >> 2);
- zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + (tmp >> 1);
+ /*
+ * Set the kswapd watermarks distance according to the
+ * scale factor in proportion to available memory, but
+ * ensure a minimum size on small systems.
+ */
+ tmp = max_t(u64, tmp >> 2,
+ mult_frac(zone->managed_pages,
+ watermark_scale_factor, 10000));
+
+ zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + tmp;
+ zone->watermark[WMARK_HIGH] = min_wmark_pages(zone) + tmp * 2;
__mod_zone_page_state(zone, NR_ALLOC_BATCH,
high_wmark_pages(zone) - low_wmark_pages(zone) -
@@ -6489,6 +6499,21 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *table, int write,
return 0;
}
+int watermark_scale_factor_sysctl_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos)
+{
+ int rc;
+
+ rc = proc_dointvec_minmax(table, write, buffer, length, ppos);
+ if (rc)
+ return rc;
+
+ if (write)
+ setup_per_zone_wmarks();
+
+ return 0;
+}
+
#ifdef CONFIG_NUMA
int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *length, loff_t *ppos)