Add a background scanning timer to restore the watermarks to the pages_lots
level and only call on it if kswapd has not been called upon for the last 5
seconds. This allows us to balance all zones to the more generous pages_lots
watermark at a time unrelated to page allocation thus leading to lighter
levels of vm load when called upon under page allocation.
Signed-off-by: Con Kolivas <[email protected]>
include/linux/mmzone.h | 2 ++
mm/vmscan.c | 39 +++++++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+)
Index: linux-ck-dev/include/linux/mmzone.h
===================================================================
--- linux-ck-dev.orig/include/linux/mmzone.h 2006-06-18 15:25:02.000000000 +1000
+++ linux-ck-dev/include/linux/mmzone.h 2006-06-18 15:25:07.000000000 +1000
@@ -14,6 +14,7 @@
#include <linux/init.h>
#include <linux/seqlock.h>
#include <linux/nodemask.h>
+#include <linux/timer.h>
#include <asm/atomic.h>
#include <asm/page.h>
@@ -312,6 +313,7 @@ typedef struct pglist_data {
wait_queue_head_t kswapd_wait;
struct task_struct *kswapd;
int kswapd_max_order;
+ struct timer_list watermark_timer;
} pg_data_t;
#define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
Index: linux-ck-dev/mm/vmscan.c
===================================================================
--- linux-ck-dev.orig/mm/vmscan.c 2006-06-18 15:25:05.000000000 +1000
+++ linux-ck-dev/mm/vmscan.c 2006-06-18 15:25:07.000000000 +1000
@@ -35,6 +35,7 @@
#include <linux/notifier.h>
#include <linux/rwsem.h>
#include <linux/delay.h>
+#include <linux/timer.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -1244,6 +1245,8 @@ out:
return nr_reclaimed;
}
+#define WT_EXPIRY (HZ * 5) /* Time to wakeup watermark_timer */
+
/*
* The background pageout daemon, started as a kernel thread
* from the init process.
@@ -1294,6 +1297,8 @@ static int kswapd(void *p)
try_to_freeze();
+ /* kswapd has been busy so delay watermark_timer */
+ mod_timer(&pgdat->watermark_timer, jiffies + WT_EXPIRY);
prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
new_order = pgdat->kswapd_max_order;
pgdat->kswapd_max_order = 0;
@@ -1517,12 +1522,41 @@ static int cpu_callback(struct notifier_
}
#endif /* CONFIG_HOTPLUG_CPU */
+/*
+ * We wake up kswapd every WT_EXPIRY till free ram is above pages_lots
+ */
+static void watermark_wakeup(unsigned long data)
+{
+ pg_data_t *pgdat = (pg_data_t *)data;
+ struct timer_list *wt = &pgdat->watermark_timer;
+ int i;
+
+ if (!waitqueue_active(&pgdat->kswapd_wait) || above_background_load())
+ goto out;
+ for (i = pgdat->nr_zones - 1; i >= 0; i--) {
+ struct zone *z = pgdat->node_zones + i;
+
+ if (!populated_zone(z) || is_highmem(z)) {
+ /* We are better off leaving highmem full */
+ continue;
+ }
+ if (!zone_watermark_ok(z, 0, z->pages_lots, 0, 0)) {
+ wake_up_interruptible(&pgdat->kswapd_wait);
+ goto out;
+ }
+ }
+out:
+ mod_timer(wt, jiffies + WT_EXPIRY);
+ return;
+}
+
static int __init kswapd_init(void)
{
pg_data_t *pgdat;
swap_setup();
for_each_online_pgdat(pgdat) {
+ struct timer_list *wt = &pgdat->watermark_timer;
pid_t pid;
pid = kernel_thread(kswapd, pgdat, CLONE_KERNEL);
@@ -1530,6 +1564,11 @@ static int __init kswapd_init(void)
read_lock(&tasklist_lock);
pgdat->kswapd = find_task_by_pid(pid);
read_unlock(&tasklist_lock);
+ init_timer(wt);
+ wt->data = (unsigned long)pgdat;
+ wt->function = watermark_wakeup;
+ wt->expires = jiffies + WT_EXPIRY;
+ add_timer(wt);
}
total_memory = nr_free_pagecache_pages();
hotcpu_notifier(cpu_callback, 0);
--
-ck
-
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