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Subject[PATCH 07/29] 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>
---
include/linux/mmzone.h | 3 +
mm/page_alloc.c | 82 +++++++++++++++++++++++++++++++++++++++++++------
mm/vmstat.c | 6 +--
3 files changed, 78 insertions(+), 13 deletions(-)
Index: linux-2.6/include/linux/mmzone.h
===================================================================
--- linux-2.6.orig/include/linux/mmzone.h
+++ linux-2.6/include/linux/mmzone.h
@@ -213,7 +213,7 @@ enum zone_type {

struct zone {
/* Fields commonly accessed by the page allocator */
- unsigned long pages_min, pages_low, pages_high;
+ unsigned long pages_emerg, pages_min, pages_low, pages_high;
/*
* 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
@@ -682,6 +682,7 @@ int sysctl_min_unmapped_ratio_sysctl_han
struct file *, void __user *, size_t *, loff_t *);
int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
struct file *, void __user *, size_t *, loff_t *);
+int adjust_memalloc_reserve(int pages);

extern int numa_zonelist_order_handler(struct ctl_table *, int,
struct file *, void __user *, size_t *, loff_t *);
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -118,6 +118,8 @@ static char * const zone_names[MAX_NR_ZO

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

unsigned long __meminitdata nr_kernel_pages;
unsigned long __meminitdata nr_all_pages;
@@ -1252,7 +1254,7 @@ int zone_watermark_ok(struct zone *z, in
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 */
@@ -1733,8 +1735,8 @@ nofail_alloc:
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();
}
@@ -1952,9 +1954,9 @@ void show_free_areas(void)
"\n",
zone->name,
K(zone_page_state(zone, NR_FREE_PAGES)),
- K(zone->pages_min),
- K(zone->pages_low),
- K(zone->pages_high),
+ K(zone->pages_emerg + zone->pages_min),
+ K(zone->pages_emerg + zone->pages_low),
+ K(zone->pages_emerg + zone->pages_high),
K(zone_page_state(zone, NR_ACTIVE)),
K(zone_page_state(zone, NR_INACTIVE)),
K(zone->present_pages),
@@ -4113,7 +4115,7 @@ static void calculate_totalreserve_pages
}

/* we treat pages_high as reserved pages. */
- max += zone->pages_high;
+ max += zone->pages_high + zone->pages_emerg;

if (max > zone->present_pages)
max = zone->present_pages;
@@ -4170,7 +4172,8 @@ static void setup_per_zone_lowmem_reserv
*/
static void __setup_per_zone_pages_min(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;
@@ -4182,11 +4185,13 @@ static void __setup_per_zone_pages_min(v
}

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

spin_lock_irqsave(&zone->lru_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
@@ -4205,12 +4210,14 @@ static void __setup_per_zone_pages_min(v
if (min_pages > 128)
min_pages = 128;
zone->pages_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->pages_min = tmp;
+ zone->pages_emerg = tmp_emerg;
}

zone->pages_low = zone->pages_min + (tmp >> 2);
@@ -4232,6 +4239,63 @@ void setup_per_zone_pages_min(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_pages_min();
+}
+
+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.
*
Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c
+++ linux-2.6/mm/vmstat.c
@@ -752,9 +752,9 @@ static void zoneinfo_show_print(struct s
"\n spanned %lu"
"\n present %lu",
zone_page_state(zone, NR_FREE_PAGES),
- zone->pages_min,
- zone->pages_low,
- zone->pages_high,
+ zone->pages_emerg + zone->pages_min,
+ zone->pages_emerg + zone->pages_low,
+ zone->pages_emerg + zone->pages_high,
zone->pages_scanned,
zone->nr_scan_active, zone->nr_scan_inactive,
zone->spanned_pages,
--



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