Messages in this thread Patch in this message | | | From | Mel Gorman <> | Subject | [PATCH 6/7] Fragmentation Avoidance V16: 006_percpu | Date | Wed, 5 Oct 2005 15:46:17 +0100 (IST) |
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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_USER 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
Now, a kernel page is in the middle of a __GFP_USER page. 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 Kernel and User lists. RCLM_NORCLM and RCLM_KERN use the Kernel list and RCLM_USER uses the user list. Strictly speaking, there should be three lists but as little effort is made to reclaim RCLM_KERN pages, it is not worth the overhead *yet*.
Signed-off-by: Mel Gorman <mel@csn.ul.ie> diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.14-rc3-005_fallback/include/linux/mmzone.h linux-2.6.14-rc3-006_percpu/include/linux/mmzone.h --- linux-2.6.14-rc3-005_fallback/include/linux/mmzone.h 2005-10-05 12:16:05.000000000 +0100 +++ linux-2.6.14-rc3-006_percpu/include/linux/mmzone.h 2005-10-05 12:26:56.000000000 +0100 @@ -55,12 +55,17 @@ struct zone_padding { #define ZONE_PADDING(name) #endif +/* Indices into pcpu_list */ +#define PCPU_KERNEL 0 +#define PCPU_USER 1 +#define PCPU_TYPES 2 + struct per_cpu_pages { - int count; /* number of pages in the list */ + int count[PCPU_TYPES]; /* Number of pages on each list */ 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[PCPU_TYPES]; /* the lists of pages */ }; struct per_cpu_pageset { @@ -75,6 +80,10 @@ struct per_cpu_pageset { #endif } ____cacheline_aligned_in_smp; +/* Helpers for per_cpu_pages */ +#define pset_count(pset) (pset.count[PCPU_KERNEL] + pset.count[PCPU_USER]) +#define for_each_pcputype(pindex) \ + for (pindex=0; pindex < RCLM_TYPES; pindex++) #ifdef CONFIG_NUMA #define zone_pcp(__z, __cpu) ((__z)->pageset[(__cpu)]) #else diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.14-rc3-005_fallback/mm/page_alloc.c linux-2.6.14-rc3-006_percpu/mm/page_alloc.c --- linux-2.6.14-rc3-005_fallback/mm/page_alloc.c 2005-10-05 12:16:05.000000000 +0100 +++ linux-2.6.14-rc3-006_percpu/mm/page_alloc.c 2005-10-05 12:27:48.000000000 +0100 @@ -780,7 +780,7 @@ 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); @@ -796,9 +796,16 @@ 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_pcputype(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); @@ -809,7 +816,7 @@ 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; @@ -819,8 +826,16 @@ 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_pcputype(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); + } } } } @@ -902,6 +917,7 @@ static void fastcall free_hot_cold_page( struct zone *zone = page_zone(page); struct per_cpu_pages *pcp; unsigned long flags; + int pindex; arch_free_page(page, 0); @@ -911,11 +927,21 @@ static void fastcall free_hot_cold_page( page->mapping = NULL; free_pages_check(__FUNCTION__, page); pcp = &zone_pcp(zone, get_cpu())->pcp[cold]; + + /* + * Strictly speaking, we should not be accessing the zone information + * here. In this case, it does not matter if the read is incorrect + */ + if (get_pageblock_type(zone, page) == RCLM_USER) + pindex = PCPU_USER; + else + pindex = PCPU_KERNEL; 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(); } @@ -954,18 +980,25 @@ buffered_rmqueue(struct zone *zone, int if (order == 0) { struct per_cpu_pages *pcp; - + int pindex = PCPU_KERNEL; + if (alloctype == RCLM_USER) + pindex = PCPU_USER; + 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, - alloctype); - if (pcp->count) { - page = list_entry(pcp->list.next, struct page, lru); + if (pcp->count[pindex] <= pcp->low) + pcp->count[pindex] += rmqueue_bulk(zone, + 0, pcp->batch, + &(pcp->list[pindex]), + alloctype); + + if (pcp->count[pindex]) { + page = list_entry(pcp->list[pindex].next, + struct page, lru); list_del(&page->lru); - pcp->count--; + pcp->count[pindex]--; } + local_irq_restore(flags); put_cpu(); } @@ -1601,7 +1634,7 @@ void show_free_areas(void) pageset->pcp[temperature].low, pageset->pcp[temperature].high, pageset->pcp[temperature].batch, - pageset->pcp[temperature].count); + pset_count(pageset->pcp[temperature])); } } @@ -2039,18 +2072,22 @@ inline void setup_pageset(struct per_cpu struct per_cpu_pages *pcp; pcp = &p->pcp[0]; /* hot */ - pcp->count = 0; + pcp->count[PCPU_KERNEL] = 0; + pcp->count[PCPU_USER] = 0; pcp->low = 2 * batch; - pcp->high = 6 * batch; + pcp->high = 3 * batch; pcp->batch = max(1UL, 1 * batch); - INIT_LIST_HEAD(&pcp->list); + INIT_LIST_HEAD(&pcp->list[PCPU_KERNEL]); + INIT_LIST_HEAD(&pcp->list[PCPU_USER]); pcp = &p->pcp[1]; /* cold*/ - pcp->count = 0; + pcp->count[PCPU_KERNEL] = 0; + pcp->count[PCPU_USER] = 0; pcp->low = 0; - pcp->high = 2 * batch; + pcp->high = batch; pcp->batch = max(1UL, 1 * batch); - INIT_LIST_HEAD(&pcp->list); + INIT_LIST_HEAD(&pcp->list[PCPU_KERNEL]); + INIT_LIST_HEAD(&pcp->list[PCPU_USER]); } #ifdef CONFIG_NUMA @@ -2460,7 +2497,7 @@ static int zoneinfo_show(struct seq_file pageset = zone_pcp(zone, i); for (j = 0; j < ARRAY_SIZE(pageset->pcp); j++) { - if (pageset->pcp[j].count) + if (pset_count(pageset->pcp[j])) break; } if (j == ARRAY_SIZE(pageset->pcp)) @@ -2473,7 +2510,7 @@ static int zoneinfo_show(struct seq_file "\n high: %i" "\n batch: %i", i, j, - pageset->pcp[j].count, + pset_count(pageset->pcp[j]), pageset->pcp[j].low, pageset->pcp[j].high, pageset->pcp[j].batch); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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