[PATCH 3/5] Light fragmentation avoidance without usemap: 003_percpu

Mel Gorman
2005-11-22T19:17:28Z

The freelists for each allocation type can slowly become corrupted due to
the per-cpu list. Consider what happens when the following happens

1. A 2^(MAX_ORDER-1) list is reserved for __GFP_EASYRCLM pages
2. An order-0 page is allocated from the newly reserved block
3. The page is freed and placed on the per-cpu list
4. alloc_page() is called with GFP_KERNEL as the gfp_mask
5. The per-cpu list is used to satisfy the allocation

This results in a kernel page is in the middle of a RCLM_EASY region. This
means that over long periods of the time, the anti-fragmentation scheme
slowly degrades to the standard allocator.

This patch divides the per-cpu lists into RCLM_TYPES number of lists.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.15-rc1-mm2-002_fragcore/include/linux/mmzone.h linux-2.6.15-rc1-mm2-003_percpu/include/linux/mmzone.h
--- linux-2.6.15-rc1-mm2-002_fragcore/include/linux/mmzone.h 2005-11-22 16:50:09.000000000 +0000
+++ linux-2.6.15-rc1-mm2-003_percpu/include/linux/mmzone.h 2005-11-22 16:52:10.000000000 +0000
@@ -26,6 +26,8 @@
#define RCLM_EASY 1
#define RCLM_TYPES 2

+#define for_each_rclmtype(type) \
+ for (type = 0; type < RCLM_TYPES; type++)
#define for_each_rclmtype_order(type, order) \
for (order = 0; order < MAX_ORDER; order++) \
for (type = 0; type < RCLM_TYPES; type++)
@@ -53,11 +55,11 @@ struct zone_padding {
#endif

struct per_cpu_pages {
- int count; /* number of pages in the list */
+ int count[RCLM_TYPES]; /* Number of pages on the lists */
int low; /* low watermark, refill needed */
int high; /* high watermark, emptying needed */
int batch; /* chunk size for buddy add/remove */
- struct list_head list; /* the list of pages */
+ struct list_head list[RCLM_TYPES]; /* the lists of pages */
};

struct per_cpu_pageset {
@@ -72,6 +74,11 @@ struct per_cpu_pageset {
#endif
} ____cacheline_aligned_in_smp;

+static inline int pcp_count(struct per_cpu_pages *pcp)
+{
+ return pcp->count[RCLM_NORCLM] + pcp->count[RCLM_EASY];
+}
+
#ifdef CONFIG_NUMA
#define zone_pcp(__z, __cpu) ((__z)->pageset[(__cpu)])
#else
diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.15-rc1-mm2-002_fragcore/mm/page_alloc.c linux-2.6.15-rc1-mm2-003_percpu/mm/page_alloc.c
--- linux-2.6.15-rc1-mm2-002_fragcore/mm/page_alloc.c 2005-11-22 16:50:09.000000000 +0000
+++ linux-2.6.15-rc1-mm2-003_percpu/mm/page_alloc.c 2005-11-22 16:52:10.000000000 +0000
@@ -637,7 +637,7 @@ static int rmqueue_bulk(struct zone *zon
void drain_remote_pages(void)
{
struct zone *zone;
- int i;
+ int i, pindex;
unsigned long flags;

local_irq_save(flags);
@@ -653,9 +653,16 @@ void drain_remote_pages(void)
struct per_cpu_pages *pcp;

pcp = &pset->pcp[i];
- if (pcp->count)
- pcp->count -= free_pages_bulk(zone, pcp->count,
- &pcp->list, 0);
+ for_each_rclmtype(pindex) {
+ if (!pcp->count[pindex])
+ continue;
+
+ /* Try remove all pages from the pcpu list */
+ pcp->count[pindex] -=
+ free_pages_bulk(zone,
+ pcp->count[pindex],
+ &pcp->list[pindex], 0);
+ }
}
}
local_irq_restore(flags);
@@ -666,7 +673,7 @@ void drain_remote_pages(void)
static void __drain_pages(unsigned int cpu)
{
struct zone *zone;
- int i;
+ int i, pindex;

for_each_zone(zone) {
struct per_cpu_pageset *pset;
@@ -676,8 +683,16 @@ static void __drain_pages(unsigned int c
struct per_cpu_pages *pcp;

pcp = &pset->pcp[i];
- pcp->count -= free_pages_bulk(zone, pcp->count,
- &pcp->list, 0);
+ for_each_rclmtype(pindex) {
+ if (!pcp->count[pindex])
+ continue;
+
+ /* Try remove all pages from the pcpu list */
+ pcp->count[pindex] -=
+ free_pages_bulk(zone,
+ pcp->count[pindex],
+ &pcp->list[pindex], 0);
+ }
}
}
}
@@ -758,6 +773,7 @@ static void FASTCALL(free_hot_cold_page(
static void fastcall free_hot_cold_page(struct page *page, int cold)
{
struct zone *zone = page_zone(page);
+ int pindex = get_pageblock_type(page);
struct per_cpu_pages *pcp;
unsigned long flags;

@@ -773,10 +789,11 @@ static void fastcall free_hot_cold_page(

pcp = &zone_pcp(zone, get_cpu())->pcp[cold];
local_irq_save(flags);
- list_add(&page->lru, &pcp->list);
- pcp->count++;
- if (pcp->count >= pcp->high)
- pcp->count -= free_pages_bulk(zone, pcp->batch, &pcp->list, 0);
+ list_add(&page->lru, &pcp->list[pindex]);
+ pcp->count[pindex]++;
+ if (pcp->count[pindex] >= pcp->high)
+ pcp->count[pindex] -= free_pages_bulk(zone, pcp->batch,
+ &pcp->list[pindex], 0);
local_irq_restore(flags);
put_cpu();
}
@@ -820,14 +837,16 @@ again:
page = NULL;
pcp = &zone_pcp(zone, get_cpu())->pcp[cold];
local_irq_save(flags);
- if (pcp->count <= pcp->low)
- pcp->count += rmqueue_bulk(zone, 0,
- pcp->batch, &pcp->list,
+ if (pcp->count[alloctype] <= pcp->low)
+ pcp->count[alloctype] += rmqueue_bulk(zone, 0,
+ pcp->batch,
+ &pcp->list[alloctype],
alloctype);
- if (pcp->count) {
- page = list_entry(pcp->list.next, struct page, lru);
+ if (pcp->count[alloctype]) {
+ page = list_entry(pcp->list[alloctype].next,
+ struct page, lru);
list_del(&page->lru);
- pcp->count--;
+ pcp->count[alloctype]--;
}
local_irq_restore(flags);
put_cpu();
@@ -1478,7 +1497,7 @@ void show_free_areas(void)
pageset->pcp[temperature].low,
pageset->pcp[temperature].high,
pageset->pcp[temperature].batch,
- pageset->pcp[temperature].count);
+ pcp_count(&pageset->pcp[temperature]));
}
}

@@ -1920,18 +1939,23 @@ inline void setup_pageset(struct per_cpu
memset(p, 0, sizeof(*p));

pcp = &p->pcp[0]; /* hot */
- pcp->count = 0;
+ pcp->count[RCLM_NORCLM] = 0;
+ pcp->count[RCLM_EASY] = 0;
pcp->low = 0;
pcp->high = 6 * batch;
pcp->batch = max(1UL, 1 * batch);
- INIT_LIST_HEAD(&pcp->list);
+ INIT_LIST_HEAD(&pcp->list[RCLM_NORCLM]);
+ INIT_LIST_HEAD(&pcp->list[RCLM_EASY]);

pcp = &p->pcp[1]; /* cold*/
- pcp->count = 0;
+
+ pcp->count[RCLM_NORCLM] = 0;
+ pcp->count[RCLM_EASY] = 0;
pcp->low = 0;
pcp->high = 2 * batch;
pcp->batch = max(1UL, batch/2);
- INIT_LIST_HEAD(&pcp->list);
+ INIT_LIST_HEAD(&pcp->list[RCLM_NORCLM]);
+ INIT_LIST_HEAD(&pcp->list[RCLM_EASY]);
}

#ifdef CONFIG_NUMA
@@ -2328,7 +2352,7 @@ static int zoneinfo_show(struct seq_file
"\n high: %i"
"\n batch: %i",
i, j,
- pageset->pcp[j].count,
+ pcp_count(&pageset->pcp[j]),
pageset->pcp[j].low,
pageset->pcp[j].high,
pageset->pcp[j].batch);