From 1b4244647ceaad42ea6eb12899d58753d82b7727 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Sun, 6 May 2007 14:48:59 -0700 Subject: [PATCH] Use ZVC counters to establish exact size of dirtyable pages We can use the global ZVC counters to establish the exact size of the LRU and the free pages. This allows 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 pages would 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. Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page-writeback.c | 50 ++++++++++++++++++++++++++++++++++++--------- 1 file changed, 40 insertions(+), 10 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index a794945fd194..029dfad5a235 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -119,6 +119,44 @@ static void background_writeout(unsigned long _min_pages); * We make sure that the background writeout level is below the adjusted * clamping level. */ + +static unsigned long highmem_dirtyable_memory(unsigned long total) +{ +#ifdef CONFIG_HIGHMEM + int node; + unsigned long x = 0; + + 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); + } + /* + * Make sure that the number of highmem pages is never larger + * than the number of the total dirtyable memory. This can only + * occur in very strange VM situations but we want to make sure + * that this does not occur. + */ + return min(x, total); +#else + return 0; +#endif +} + +static unsigned long determine_dirtyable_memory(void) +{ + unsigned long x; + + x = global_page_state(NR_FREE_PAGES) + + global_page_state(NR_INACTIVE) + + global_page_state(NR_ACTIVE); + x -= highmem_dirtyable_memory(x); + return x + 1; /* Ensure that we never return 0 */ +} + static void get_dirty_limits(long *pbackground, long *pdirty, struct address_space *mapping) @@ -128,20 +166,12 @@ get_dirty_limits(long *pbackground, long *pdirty, 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; + available_memory; dirty_ratio = vm_dirty_ratio; if (dirty_ratio > unmapped_ratio / 2)