From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 12 Feb 2007 10:16:23 -0800 (PST) From: Christoph Lameter Subject: Use ZVC counters to establish exact size of dirtyable pages Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: akpm@osdl.org Cc: linux-mm@kvack.org List-ID: We can use the global ZVC counters to establish the exact size of the LRU and the free pages allowing a more accurate determination of the dirty ratio. This patch will fix the broken ratio calculations if large amounts of memory are allocated to huge pags or other consumers that do not put the pages on to the LRU. Notes: - I did not add NR_SLAB_RECLAIMABLE to the calculation of the dirtyable pages. Those may be reclaimable but they are at this point not dirtyable. If NR_SLAB_RECLAIMABLE would be considered then a huge number of reclaimable slab pages could stop writeback from occurring. - This patch used to be in mm as the last one in a series of patches. It was removed when Linus updated the treatment of highmem because there was a conflict. I updated the patch to follow Linus' approach. This patch is neede to fulfill the claims made in the beginning of the patchset that is now in Linus' tree. - I added an optimized path for i386 NUMA since the zone layout allows determination of the non HIGHMEM pages by adding up lowmem zones on node 0. Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Index: linux-2.6/mm/page-writeback.c =================================================================== --- linux-2.6.orig/mm/page-writeback.c 2007-02-12 09:15:22.000000000 -0800 +++ linux-2.6/mm/page-writeback.c 2007-02-12 10:06:15.000000000 -0800 @@ -119,6 +119,58 @@ static void background_writeout(unsigned * We make sure that the background writeout level is below the adjusted * clamping level. */ + +static unsigned long determine_dirtyable_memory(void) +{ + unsigned long x; + +#ifndef CONFIG_HIGHMEM + x = global_page_state(NR_FREE_PAGES) + + global_page_state(NR_INACTIVE) + + global_page_state(NR_ACTIVE); +#else + /* + * We always exclude high memory from our count + */ +#if defined(CONFIG_NUMA) && defined(CONFIG_X86_32) + /* + * i386 32 bit NUMA configurations have all non HIGHMEM zones on + * node 0. So its easier to just add up the lowmemt zones on node 0. + */ + struct zone * z; + + x = 0; + for (z = NODE_DATA(0)->node_zones; + z < NODE_DATA(0)->node_zones + ZONE_HIGHMEM; + z++) + x = zone_page_state(z, NR_FREE_PAGES) + + zone_page_state(z, NR_INACTIVE) + + zone_page_state(z, NR_ACTIVE); + +#else + /* + * Just subtract the HIGHMEM zones. + */ + int node; + + x = global_page_state(NR_FREE_PAGES) + + global_page_state(NR_INACTIVE) + + global_page_state(NR_ACTIVE); + + for_each_online_node(node) { + struct zone *z = + &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; + + x -= zone_page_state(z, NR_FREE_PAGES) + + zone_page_state(z, NR_INACTIVE) + + zone_page_state(z, NR_ACTIVE); + } + +#endif +#endif /* CONFIG_HIGHMEM */ + return x; +} + static void get_dirty_limits(long *pbackground, long *pdirty, struct address_space *mapping) @@ -128,17 +180,9 @@ get_dirty_limits(long *pbackground, long int unmapped_ratio; long background; long dirty; - unsigned long available_memory = vm_total_pages; + unsigned long available_memory = determine_dirtyable_memory(); struct task_struct *tsk; -#ifdef CONFIG_HIGHMEM - /* - * We always exclude high memory from our count. - */ - available_memory -= totalhigh_pages; -#endif - - unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) + global_page_state(NR_ANON_PAGES)) * 100) / vm_total_pages; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org