Make dirty throttling obey cpusets Currently dirty throttling does not work properly in a cpuset. If f.e a cpuset contains only 1/10th of available memory then all of the memory of a cpuset can be dirtied without any writes being triggered. If all of the cpusets memory is dirty then only 10% of memory is dirty. The background writeback threshold is usually set at 40% and the synchrononous threshold at 60%. So we are still below the global limits while the dirty ratio in the cpuset is 100%! F.e. NFS pages can fill up the complete cpuset. This patch makes dirty writeout cpuset aware. When determining the dirty limits in get_dirty_limits() we calculate values based on the nodes that are reachable from the current process (that has been dirtying the page). Then we can trigger writeout based on the dirty ratio of the memory in the cpuset. Determination of the dirty state is expensive since we have to scan over all the nodes and sum up the relevant values. We trigger writeout in a a cpuset specific way. We go through the dirty inodes and search for pages that fit the node requirements. For that purpose we have to extend the write_control structure to contain a nodemask. Christoph Lameter Index: linux-2.6.20-rc3/mm/page-writeback.c =================================================================== --- linux-2.6.20-rc3.orig/mm/page-writeback.c 2007-01-03 11:21:40.000000000 -0800 +++ linux-2.6.20-rc3/mm/page-writeback.c 2007-01-03 11:32:01.000000000 -0800 @@ -33,6 +33,7 @@ #include #include #include +#include /* * The maximum number of pages to writeout in a single bdflush/kupdate @@ -102,6 +103,15 @@ static void background_writeout(unsigned long _min_pages); +struct dirty_limits { + long thresh_background; + long thresh_dirty; + unsigned long nr_dirty; + unsigned long nr_unstable; + unsigned long nr_writeback; + nodemask_t *nodes; +}; + /* * Work out the current dirty-memory clamping and background writeout * thresholds. @@ -120,30 +130,64 @@ * clamping level. */ static void -get_dirty_limits(long *pbackground, long *pdirty, - struct address_space *mapping) +get_dirty_limits(struct dirty_limits *dl, struct address_space *mapping) { int background_ratio; /* Percentages */ int dirty_ratio; int unmapped_ratio; long background; long dirty; - unsigned long available_memory = vm_total_pages; + unsigned long available_memory; + unsigned long high_memory; + unsigned long nr_mapped; struct task_struct *tsk; + /* + * Respect the boundaries of the current cpuset otherwise dirty + * writeout will not work properly in a cpuset. + */ + if (likely(!nodes_equal(node_online_map, cpuset_current_mems_allowed))) { + dl->nr_dirty = global_page_state(NR_FILE_DIRTY); + dl->nr_unstable = global_page_state(NR_UNSTABLE_NFS); + dl->nr_writeback = global_page_state(NR_WRITEBACK); + available_memory = vm_total_pages; + high_memory = totalhigh_pages; + nr_mapped = global_page_state(NR_FILE_MAPPED) + + global_page_state(NR_ANON_PAGES); + dl->nodes = NULL; + } else { + int node; + + memset(&dl, 0, sizeof(struct dirty_limits)); + available_memory = 0; + high_memory = 0; + nr_mapped = 0; + + for_each_node_mask(node, cpuset_current_mems_allowed) { + dl->nr_dirty += node_page_state(node, NR_FILE_DIRTY); + dl->nr_unstable += node_page_state(node, NR_UNSTABLE_NFS); + dl->nr_writeback += node_page_state(node, NR_WRITEBACK); + available_memory += NODE_DATA(node)->node_present_pages; +#ifdef CONFIG_HIGHMEM + high_memory += NODE_DATA(node)->node_zones[ZONE_HIGHMEM]->present_pages; +#endif + nr_mapped += node_page_state(node, NR_FILE_MAPPED) + + node_page_state(node, NR_ANON_PAGES); + } + dl->nodes = &cpuset_current_mems_allowed; + } + #ifdef CONFIG_HIGHMEM /* * If this mapping can only allocate from low memory, * we exclude high memory from our count. */ if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM)) - available_memory -= totalhigh_pages; + available_memory -= high_memory; #endif - unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) + - global_page_state(NR_ANON_PAGES)) * 100) / - vm_total_pages; + unmapped_ratio = 100 - (nr_mapped * 100) / vm_total_pages; dirty_ratio = vm_dirty_ratio; if (dirty_ratio > unmapped_ratio / 2) @@ -163,8 +207,8 @@ background += background / 4; dirty += dirty / 4; } - *pbackground = background; - *pdirty = dirty; + dl->thresh_background = background; + dl->thresh_dirty = dirty; } /* @@ -177,8 +221,7 @@ static void balance_dirty_pages(struct address_space *mapping) { long nr_reclaimable; - long background_thresh; - long dirty_thresh; + struct dirty_limits dl; unsigned long pages_written = 0; unsigned long write_chunk = sync_writeback_pages(); @@ -193,11 +236,11 @@ .range_cyclic = 1, }; - get_dirty_limits(&background_thresh, &dirty_thresh, mapping); - nr_reclaimable = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS); - if (nr_reclaimable + global_page_state(NR_WRITEBACK) <= - dirty_thresh) + get_dirty_limits(&dl, mapping); + wbc.nodes = dl.nodes; + nr_reclaimable = dl.nr_dirty + dl.nr_unstable; + if (nr_reclaimable + dl.nr_writeback <= + dl.thresh_dirty) break; if (!dirty_exceeded) @@ -211,13 +254,9 @@ */ if (nr_reclaimable) { writeback_inodes(&wbc); - get_dirty_limits(&background_thresh, - &dirty_thresh, mapping); - nr_reclaimable = global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS); - if (nr_reclaimable + - global_page_state(NR_WRITEBACK) - <= dirty_thresh) + get_dirty_limits(&dl, mapping); + nr_reclaimable = dl.nr_dirty + dl.nr_unstable; + if (nr_reclaimable + dl.nr_writeback <= dl.thresh_dirty) break; pages_written += write_chunk - wbc.nr_to_write; if (pages_written >= write_chunk) @@ -226,8 +265,8 @@ congestion_wait(WRITE, HZ/10); } - if (nr_reclaimable + global_page_state(NR_WRITEBACK) - <= dirty_thresh && dirty_exceeded) + if (nr_reclaimable + dl.nr_writeback + <= dl.thresh_dirty && dirty_exceeded) dirty_exceeded = 0; if (writeback_in_progress(bdi)) @@ -242,7 +281,7 @@ * background_thresh, to keep the amount of dirty memory low. */ if ((laptop_mode && pages_written) || - (!laptop_mode && (nr_reclaimable > background_thresh))) + (!laptop_mode && (nr_reclaimable > dl.thresh_background))) pdflush_operation(background_writeout, 0); } @@ -300,21 +339,19 @@ void throttle_vm_writeout(void) { - long background_thresh; - long dirty_thresh; + struct dirty_limits dl; for ( ; ; ) { - get_dirty_limits(&background_thresh, &dirty_thresh, NULL); + get_dirty_limits(&dl, NULL); /* * Boost the allowable dirty threshold a bit for page * allocators so they don't get DoS'ed by heavy writers */ - dirty_thresh += dirty_thresh / 10; /* wheeee... */ + dl.thresh_dirty += dl.thresh_dirty / 10; /* wheeee... */ - if (global_page_state(NR_UNSTABLE_NFS) + - global_page_state(NR_WRITEBACK) <= dirty_thresh) - break; + if (dl.nr_unstable + dl.nr_writeback <= dl.thresh_dirty) + break; congestion_wait(WRITE, HZ/10); } } @@ -337,12 +374,11 @@ }; for ( ; ; ) { - long background_thresh; - long dirty_thresh; + struct dirty_limits dl; - get_dirty_limits(&background_thresh, &dirty_thresh, NULL); - if (global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS) < background_thresh + get_dirty_limits(&dl, NULL); + wbc.nodes = dl.nodes; + if (dl.nr_dirty + dl.nr_unstable < dl.thresh_background && min_pages <= 0) break; wbc.encountered_congestion = 0; @@ -407,6 +443,7 @@ .nonblocking = 1, .for_kupdate = 1, .range_cyclic = 1, + .nodes = &cpuset_current_mems_allowed, }; sync_supers(); Index: linux-2.6.20-rc3/include/linux/writeback.h =================================================================== --- linux-2.6.20-rc3.orig/include/linux/writeback.h 2007-01-03 11:21:40.000000000 -0800 +++ linux-2.6.20-rc3/include/linux/writeback.h 2007-01-03 11:23:52.000000000 -0800 @@ -41,6 +41,7 @@ enum writeback_sync_modes sync_mode; unsigned long *older_than_this; /* If !NULL, only write back inodes older than this */ + nodemask_t *nodes; /* Restrict writeback to these nodes */ long nr_to_write; /* Write this many pages, and decrement this for each page written */ long pages_skipped; /* Pages which were not written */ Index: linux-2.6.20-rc3/fs/fs-writeback.c =================================================================== --- linux-2.6.20-rc3.orig/fs/fs-writeback.c 2007-01-03 11:23:20.000000000 -0800 +++ linux-2.6.20-rc3/fs/fs-writeback.c 2007-01-03 11:23:52.000000000 -0800 @@ -368,6 +368,10 @@ if (current_is_pdflush() && !writeback_acquire(bdi)) break; +#ifdef CONFIG_NUMA + if (wbc->nodes && !nodes_intersects(mapping->dirty_map, *wbc->nodes)) + break; +#endif BUG_ON(inode->i_state & I_FREEING); __iget(inode); pages_skipped = wbc->pages_skipped;