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Subject[PATCH -mmotm 08/30] mm: emergency pool
From 973ce2ee797025f055ccb61359180e53c3ecc681 Mon Sep 17 00:00:00 2001
From: Xiaotian Feng <dfeng@redhat.com>
Date: Tue, 13 Jul 2010 10:45:48 +0800
Subject: [PATCH 08/30] mm: emergency pool

Provide means to reserve a specific amount of pages.

The emergency pool is separated from the min watermark because ALLOC_HARDER
and ALLOC_HIGH modify the watermark in a relative way and thus do not ensure
a strict minimum.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
---
include/linux/mmzone.h | 3 ++
mm/page_alloc.c | 84 ++++++++++++++++++++++++++++++++++++++++++------
mm/vmstat.c | 6 ++--
3 files changed, 80 insertions(+), 13 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9ed9c45..75a0871 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -279,6 +279,7 @@ struct zone_reclaim_stat {

struct zone {
/* Fields commonly accessed by the page allocator */
+ unsigned long pages_emerg; /* emergency pool */

/* zone watermarks, access with *_wmark_pages(zone) macros */
unsigned long watermark[NR_WMARK];
@@ -770,6 +771,8 @@ int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,
int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);

+int adjust_memalloc_reserve(int pages);
+
extern int numa_zonelist_order_handler(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern char numa_zonelist_order[];
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4b1fa10..6c85e9e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -167,6 +167,8 @@ static char * const zone_names[MAX_NR_ZONES] = {

static DEFINE_SPINLOCK(min_free_lock);
int min_free_kbytes = 1024;
+static DEFINE_MUTEX(var_free_mutex);
+int var_free_kbytes;

static unsigned long __meminitdata nr_kernel_pages;
static unsigned long __meminitdata nr_all_pages;
@@ -1457,7 +1459,7 @@ int zone_watermark_ok(struct zone *z, int order, unsigned long mark,
if (alloc_flags & ALLOC_HARDER)
min -= min / 4;

- if (free_pages <= min + z->lowmem_reserve[classzone_idx])
+ if (free_pages <= min+z->lowmem_reserve[classzone_idx]+z->pages_emerg)
return 0;
for (o = 0; o < order; o++) {
/* At the next order, this order's pages become unavailable */
@@ -1946,7 +1948,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
{
const gfp_t wait = gfp_mask & __GFP_WAIT;
struct page *page = NULL;
- int alloc_flags;
+ int alloc_flags = 0;
unsigned long pages_reclaimed = 0;
unsigned long did_some_progress;
struct task_struct *p = current;
@@ -2078,8 +2080,8 @@ rebalance:
nopage:
if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit()) {
printk(KERN_WARNING "%s: page allocation failure."
- " order:%d, mode:0x%x\n",
- p->comm, order, gfp_mask);
+ " order:%d, mode:0x%x, alloc_flags:0x%x, pflags:0x%x\n",
+ p->comm, order, gfp_mask, alloc_flags, p->flags);
dump_stack();
show_mem();
}
@@ -2414,9 +2416,9 @@ void show_free_areas(void)
"\n",
zone->name,
K(zone_page_state(zone, NR_FREE_PAGES)),
- K(min_wmark_pages(zone)),
- K(low_wmark_pages(zone)),
- K(high_wmark_pages(zone)),
+ K(zone->pages_emerg + min_wmark_pages(zone)),
+ K(zone->pages_emerg + low_wmark_pages(zone)),
+ K(zone->pages_emerg + high_wmark_pages(zone)),
K(zone_page_state(zone, NR_ACTIVE_ANON)),
K(zone_page_state(zone, NR_INACTIVE_ANON)),
K(zone_page_state(zone, NR_ACTIVE_FILE)),
@@ -4779,7 +4781,7 @@ static void calculate_totalreserve_pages(void)
}

/* we treat the high watermark as reserved pages. */
- max += high_wmark_pages(zone);
+ max += high_wmark_pages(zone) + zone->pages_emerg;

if (max > zone->present_pages)
max = zone->present_pages;
@@ -4837,7 +4839,8 @@ static void setup_per_zone_lowmem_reserve(void)
*/
static void __setup_per_zone_wmarks(void)
{
- unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
+ unsigned pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
+ unsigned pages_emerg = var_free_kbytes >> (PAGE_SHIFT - 10);
unsigned long lowmem_pages = 0;
struct zone *zone;
unsigned long flags;
@@ -4849,11 +4852,13 @@ static void __setup_per_zone_wmarks(void)
}

for_each_zone(zone) {
- u64 tmp;
+ u64 tmp, tmp_emerg;

spin_lock_irqsave(&zone->lock, flags);
tmp = (u64)pages_min * zone->present_pages;
do_div(tmp, lowmem_pages);
+ tmp_emerg = (u64)pages_emerg * zone->present_pages;
+ do_div(tmp_emerg, lowmem_pages);
if (is_highmem(zone)) {
/*
* __GFP_HIGH and PF_MEMALLOC allocations usually don't
@@ -4872,12 +4877,14 @@ static void __setup_per_zone_wmarks(void)
if (min_pages > 128)
min_pages = 128;
zone->watermark[WMARK_MIN] = min_pages;
+ zone->pages_emerg = 0;
} else {
/*
* If it's a lowmem zone, reserve a number of pages
* proportionate to the zone's size.
*/
zone->watermark[WMARK_MIN] = tmp;
+ zone->pages_emerg = tmp_emerg;
}

zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + (tmp >> 2);
@@ -4942,6 +4949,63 @@ void setup_per_zone_wmarks(void)
spin_unlock_irqrestore(&min_free_lock, flags);
}

+static void __adjust_memalloc_reserve(int pages)
+{
+ var_free_kbytes += pages << (PAGE_SHIFT - 10);
+ BUG_ON(var_free_kbytes < 0);
+ setup_per_zone_wmarks();
+}
+
+static int test_reserve_limits(void)
+{
+ struct zone *zone;
+ int node;
+
+ for_each_zone(zone)
+ wakeup_kswapd(zone, 0);
+
+ for_each_online_node(node) {
+ struct page *page = alloc_pages_node(node, GFP_KERNEL, 0);
+ if (!page)
+ return -ENOMEM;
+
+ __free_page(page);
+ }
+
+ return 0;
+}
+
+/**
+ * adjust_memalloc_reserve - adjust the memalloc reserve
+ * @pages: number of pages to add
+ *
+ * It adds a number of pages to the memalloc reserve; if
+ * the number was positive it kicks reclaim into action to
+ * satisfy the higher watermarks.
+ *
+ * returns -ENOMEM when it failed to satisfy the watermarks.
+ */
+int adjust_memalloc_reserve(int pages)
+{
+ int err = 0;
+
+ mutex_lock(&var_free_mutex);
+ __adjust_memalloc_reserve(pages);
+ if (pages > 0) {
+ err = test_reserve_limits();
+ if (err) {
+ __adjust_memalloc_reserve(-pages);
+ goto unlock;
+ }
+ }
+ printk(KERN_DEBUG "Emergency reserve: %d\n", var_free_kbytes);
+
+unlock:
+ mutex_unlock(&var_free_mutex);
+ return err;
+}
+EXPORT_SYMBOL_GPL(adjust_memalloc_reserve);
+
/*
* Initialise min_free_kbytes.
*
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 15a14b1..af91d5c 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -814,9 +814,9 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
"\n spanned %lu"
"\n present %lu",
zone_page_state(zone, NR_FREE_PAGES),
- min_wmark_pages(zone),
- low_wmark_pages(zone),
- high_wmark_pages(zone),
+ zone->pages_emerg + min_wmark_pages(zone),
+ zone->pages_emerg + min_wmark_pages(zone),
+ zone->pages_emerg + high_wmark_pages(zone),
zone->pages_scanned,
zone->spanned_pages,
zone->present_pages);
--
1.7.1.1


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