From 9feedc9d831e18ae6d0d15aa562e5e46ba53647b Mon Sep 17 00:00:00 2001 From: Jiang Liu Date: Wed, 12 Dec 2012 13:52:12 -0800 Subject: mm: introduce new field "managed_pages" to struct zone Currently a zone's present_pages is calcuated as below, which is inaccurate and may cause trouble to memory hotplug. spanned_pages - absent_pages - memmap_pages - dma_reserve. During fixing bugs caused by inaccurate zone->present_pages, we found zone->present_pages has been abused. The field zone->present_pages may have different meanings in different contexts: 1) pages existing in a zone. 2) pages managed by the buddy system. For more discussions about the issue, please refer to: http://lkml.org/lkml/2012/11/5/866 https://patchwork.kernel.org/patch/1346751/ This patchset tries to introduce a new field named "managed_pages" to struct zone, which counts "pages managed by the buddy system". And revert zone->present_pages to count "physical pages existing in a zone", which also keep in consistence with pgdat->node_present_pages. We will set an initial value for zone->managed_pages in function free_area_init_core() and will adjust it later if the initial value is inaccurate. For DMA/normal zones, the initial value is set to: (spanned_pages - absent_pages - memmap_pages - dma_reserve) Later zone->managed_pages will be adjusted to the accurate value when the bootmem allocator frees all free pages to the buddy system in function free_all_bootmem_node() and free_all_bootmem(). The bootmem allocator doesn't touch highmem pages, so highmem zones' managed_pages is set to the accurate value "spanned_pages - absent_pages" in function free_area_init_core() and won't be updated anymore. This patch also adds a new field "managed_pages" to /proc/zoneinfo and sysrq showmem. [akpm@linux-foundation.org: small comment tweaks] Signed-off-by: Jiang Liu Cc: Wen Congyang Cc: David Rientjes Cc: Maciej Rutecki Tested-by: Chris Clayton Cc: "Rafael J . Wysocki" Cc: Mel Gorman Cc: Minchan Kim Cc: KAMEZAWA Hiroyuki Cc: Michal Hocko Cc: Jianguo Wu Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 44 ++++++++++++++++++++++++++++++-------------- 1 file changed, 30 insertions(+), 14 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2bf0d43d646b..0b6a6d04300a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -735,6 +735,13 @@ static void __free_pages_ok(struct page *page, unsigned int order) local_irq_restore(flags); } +/* + * Read access to zone->managed_pages is safe because it's unsigned long, + * but we still need to serialize writers. Currently all callers of + * __free_pages_bootmem() except put_page_bootmem() should only be used + * at boot time. So for shorter boot time, we shift the burden to + * put_page_bootmem() to serialize writers. + */ void __meminit __free_pages_bootmem(struct page *page, unsigned int order) { unsigned int nr_pages = 1 << order; @@ -750,6 +757,7 @@ void __meminit __free_pages_bootmem(struct page *page, unsigned int order) set_page_count(p, 0); } + page_zone(page)->managed_pages += 1 << order; set_page_refcounted(page); __free_pages(page, order); } @@ -2984,6 +2992,7 @@ void show_free_areas(unsigned int filter) " isolated(anon):%lukB" " isolated(file):%lukB" " present:%lukB" + " managed:%lukB" " mlocked:%lukB" " dirty:%lukB" " writeback:%lukB" @@ -3013,6 +3022,7 @@ void show_free_areas(unsigned int filter) K(zone_page_state(zone, NR_ISOLATED_ANON)), K(zone_page_state(zone, NR_ISOLATED_FILE)), K(zone->present_pages), + K(zone->managed_pages), K(zone_page_state(zone, NR_MLOCK)), K(zone_page_state(zone, NR_FILE_DIRTY)), K(zone_page_state(zone, NR_WRITEBACK)), @@ -4502,48 +4512,54 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, for (j = 0; j < MAX_NR_ZONES; j++) { struct zone *zone = pgdat->node_zones + j; - unsigned long size, realsize, memmap_pages; + unsigned long size, realsize, freesize, memmap_pages; size = zone_spanned_pages_in_node(nid, j, zones_size); - realsize = size - zone_absent_pages_in_node(nid, j, + realsize = freesize = size - zone_absent_pages_in_node(nid, j, zholes_size); /* - * Adjust realsize so that it accounts for how much memory + * Adjust freesize so that it accounts for how much memory * is used by this zone for memmap. This affects the watermark * and per-cpu initialisations */ memmap_pages = PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT; - if (realsize >= memmap_pages) { - realsize -= memmap_pages; + if (freesize >= memmap_pages) { + freesize -= memmap_pages; if (memmap_pages) printk(KERN_DEBUG " %s zone: %lu pages used for memmap\n", zone_names[j], memmap_pages); } else printk(KERN_WARNING - " %s zone: %lu pages exceeds realsize %lu\n", - zone_names[j], memmap_pages, realsize); + " %s zone: %lu pages exceeds freesize %lu\n", + zone_names[j], memmap_pages, freesize); /* Account for reserved pages */ - if (j == 0 && realsize > dma_reserve) { - realsize -= dma_reserve; + if (j == 0 && freesize > dma_reserve) { + freesize -= dma_reserve; printk(KERN_DEBUG " %s zone: %lu pages reserved\n", zone_names[0], dma_reserve); } if (!is_highmem_idx(j)) - nr_kernel_pages += realsize; - nr_all_pages += realsize; + nr_kernel_pages += freesize; + nr_all_pages += freesize; zone->spanned_pages = size; - zone->present_pages = realsize; + zone->present_pages = freesize; + /* + * Set an approximate value for lowmem here, it will be adjusted + * when the bootmem allocator frees pages into the buddy system. + * And all highmem pages will be managed by the buddy system. + */ + zone->managed_pages = is_highmem_idx(j) ? realsize : freesize; #ifdef CONFIG_NUMA zone->node = nid; - zone->min_unmapped_pages = (realsize*sysctl_min_unmapped_ratio) + zone->min_unmapped_pages = (freesize*sysctl_min_unmapped_ratio) / 100; - zone->min_slab_pages = (realsize * sysctl_min_slab_ratio) / 100; + zone->min_slab_pages = (freesize * sysctl_min_slab_ratio) / 100; #endif zone->name = zone_names[j]; spin_lock_init(&zone->lock); -- cgit v1.2.3