--- /dev/null
+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 <kernel@kolivas.org>
+
+The -ck patches modify mm/vmscan.c and add a timer to wake up kswapd every 5
+seconds. This timer is initialized after the creation of the kswapd thread.
+
+The kswapd() thread function calls mod_timer at the front of its infinite
+service loop (to reset the timer to 5 seconds in the future). mod_timer()
+includes a BUG_ON() to assert that the timer's callback function is set.
+
+Since the wakeup timer is initialized after the kswapd thread is created, if
+kswapd gets scheduled before kswapd_run() has prepared the timer, the
+BUG_ON() check will throw a stack trace and immediately terminate the kswapd
+thread.
+
+This patch modifies the kswapd_run() function in mm/vmscan.c to initialize the
+watermark timer before starting the kswapd thread.
+
+Signed-off-by: Chase Venters <chase.venters at clientec.com>
+
+ include/linux/mmzone.h | 2 ++
+ mm/vmscan.c | 42 ++++++++++++++++++++++++++++++++++++++++++
+ 2 files changed, 44 insertions(+)
+
+Index: linux-2.6.22-ck1/include/linux/mmzone.h
+===================================================================
+--- linux-2.6.22-ck1.orig/include/linux/mmzone.h 2007-07-09 18:44:40.000000000 +1000
++++ linux-2.6.22-ck1/include/linux/mmzone.h 2007-07-09 18:44:40.000000000 +1000
+@@ -13,6 +13,7 @@
+ #include <linux/init.h>
+ #include <linux/seqlock.h>
+ #include <linux/nodemask.h>
++#include <linux/timer.h>
+ #include <linux/pageblock-flags.h>
+ #include <linux/bounds.h>
+ #include <asm/atomic.h>
+@@ -452,6 +453,7 @@ 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-2.6.22-ck1/mm/vmscan.c
+===================================================================
+--- linux-2.6.22-ck1.orig/mm/vmscan.c 2007-07-09 18:44:40.000000000 +1000
++++ linux-2.6.22-ck1/mm/vmscan.c 2007-07-09 18:44:40.000000000 +1000
+@@ -37,6 +37,7 @@
+ #include <linux/rwsem.h>
+ #include <linux/delay.h>
+ #include <linux/kthread.h>
++#include <linux/timer.h>
+ #include <linux/freezer.h>
+ #include <linux/memcontrol.h>
+ #include <linux/delayacct.h>
+@@ -1330,6 +1331,8 @@ 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.
+@@ -1377,6 +1380,8 @@ static int kswapd(void *p)
+ for ( ; ; ) {
+ unsigned long new_order;
+
++ /* 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;
+@@ -1604,20 +1609,57 @@ static int __devinit cpu_callback(struct
+ }
+
+ /*
++ * 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;
++}
++
++/*
+ * This kswapd start function will be called by init and node-hot-add.
+ * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
+ */
+ int kswapd_run(int nid)
+ {
+ pg_data_t *pgdat = NODE_DATA(nid);
++ struct timer_list *wt;
+ int ret = 0;
+
+ if (pgdat->kswapd)
+ return 0;
+
++ wt = &pgdat->watermark_timer;
++ init_timer(wt);
++ wt->data = (unsigned long)pgdat;
++ wt->function = watermark_wakeup;
++ wt->expires = jiffies + WT_EXPIRY;
++ add_timer(wt);
++
+ pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
+ if (IS_ERR(pgdat->kswapd)) {
+ /* failure at boot is fatal */
++ del_timer(wt);
+ BUG_ON(system_state == SYSTEM_BOOTING);
+ printk("Failed to start kswapd on node %d\n",nid);
+ ret = -1;
+
--- /dev/null
+The vm currently performs scanning when allocating ram once the watermarks
+are below the pages_low value and tries to restore them to the pages_high
+watermark. The disadvantage of this is that we are scanning most aggresssively
+at the same time we are allocating ram regardless of the stress the vm is
+under. Add a pages_lots watermark and allow the watermark to be relaxed
+according to the stress the vm is at the time (according to the priority
+value). Thus we have more in reserve next time we are allocating ram and end
+up scanning less aggresssively. Note the actual pages_lots isn't used directly
+in this code.
+
+Signed-off-by: Con Kolivas <kernel@kolivas.org>
+
+ include/linux/mmzone.h | 2 +-
+ mm/page_alloc.c | 3 +++
+ mm/vmscan.c | 17 ++++++++++++++---
+ 3 files changed, 18 insertions(+), 4 deletions(-)
+
+Index: linux-2.6.22-ck1/include/linux/mmzone.h
+===================================================================
+--- linux-2.6.22-ck1.orig/include/linux/mmzone.h 2007-07-09 18:44:34.000000000 +1000
++++ linux-2.6.22-ck1/include/linux/mmzone.h 2007-07-09 18:44:39.000000000 +1000
+@@ -181,7 +181,7 @@ enum zone_type {
+
+ struct zone {
+ /* Fields commonly accessed by the page allocator */
+- unsigned long pages_min, pages_low, pages_high;
++ unsigned long pages_min, pages_low, pages_high, pages_lots;
+ /*
+ * We don't know if the memory that we're going to allocate will be freeable
+ * or/and it will be released eventually, so to avoid totally wasting several
+Index: linux-2.6.22-ck1/mm/page_alloc.c
+===================================================================
+--- linux-2.6.22-ck1.orig/mm/page_alloc.c 2007-07-09 18:44:34.000000000 +1000
++++ linux-2.6.22-ck1/mm/page_alloc.c 2007-07-09 18:44:39.000000000 +1000
+@@ -1570,6 +1570,7 @@ void show_free_areas(void)
+ " min:%lukB"
+ " low:%lukB"
+ " high:%lukB"
++ " lots:%lukB"
+ " active_anon:%lukB"
+ " inactive_anon:%lukB"
+ " active_file:%lukB"
+@@ -1581,6 +1582,7 @@ void show_free_areas(void)
+ K(zone->pages_min),
+ K(zone->pages_low),
+ K(zone->pages_high),
++ K(zone->pages_lots),
+ K(zone_page_state(zone, NR_ACTIVE_ANON)),
+ K(zone_page_state(zone, NR_INACTIVE_ANON)),
+ K(zone_page_state(zone, NR_ACTIVE_FILE)),
+@@ -3142,6 +3144,7 @@ void setup_per_zone_pages_min(void)
+
+ zone->pages_low = zone->pages_min + (tmp >> 2);
+ zone->pages_high = zone->pages_min + (tmp >> 1);
++ zone->pages_lots = zone->pages_min + tmp;
+ setup_zone_migrate_reserve(zone);
+ spin_unlock_irqrestore(&zone->lock, flags);
+ }
+Index: linux-2.6.22-ck1/mm/vmscan.c
+===================================================================
+--- linux-2.6.22-ck1.orig/mm/vmscan.c 2007-07-09 18:44:39.000000000 +1000
++++ linux-2.6.22-ck1/mm/vmscan.c 2007-07-09 18:44:39.000000000 +1000
+@@ -1171,6 +1171,7 @@ loop_again:
+ */
+ for (i = pgdat->nr_zones - 1; i >= 0; i--) {
+ struct zone *zone = pgdat->node_zones + i;
++ unsigned long watermark;
+
+ if (!populated_zone(zone))
+ continue;
+@@ -1178,8 +1179,14 @@ loop_again:
+ shrink_active_list(SWAP_CLUSTER_MAX, zone,
+ &sc, priority, 0);
+
+- if (!zone_watermark_ok(zone, order, zone->pages_high,
+- 0, 0)) {
++ /*
++ * The watermark is relaxed depending on the
++ * level of "priority" till it drops to
++ * pages_high.
++ */
++ watermark = zone->pages_high + (zone->pages_high *
++ priority / DEF_PRIORITY);
++ if (!zone_watermark_ok(zone, order, watermark, 0, 0)) {
+ end_zone = i;
+ break;
+ }
+@@ -1206,6 +1213,7 @@ loop_again:
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+ int nr_slab;
++ unsigned long watermark;
+
+ if (!populated_zone(zone))
+ continue;
+@@ -1213,7 +1221,10 @@ loop_again:
+ priority != DEF_PRIORITY)
+ continue;
+
+- if (!zone_watermark_ok(zone, order, zone->pages_high,
++ watermark = zone->pages_high + (zone->pages_high *
++ priority / DEF_PRIORITY);
++
++ if (!zone_watermark_ok(zone, order, watermark,
+ end_zone, 0))
+ all_zones_ok = 0;
+ temp_priority[i] = priority;
+
projects / kernel-bfs / commitdiff