diff options
| -rw-r--r-- | include/linux/gfp.h | 4 | ||||
| -rw-r--r-- | include/linux/writeback.h | 1 | ||||
| -rw-r--r-- | mm/page-writeback.c | 82 | ||||
| -rw-r--r-- | mm/page_alloc.c | 29 |
4 files changed, 115 insertions, 1 deletions
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 66f172fdf5fe..581e74b7df95 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -36,6 +36,7 @@ struct vm_area_struct; #endif #define ___GFP_NO_KSWAPD 0x400000u #define ___GFP_OTHER_NODE 0x800000u +#define ___GFP_WRITE 0x1000000u /* * GFP bitmasks.. @@ -85,6 +86,7 @@ struct vm_area_struct; #define __GFP_NO_KSWAPD ((__force gfp_t)___GFP_NO_KSWAPD) #define __GFP_OTHER_NODE ((__force gfp_t)___GFP_OTHER_NODE) /* On behalf of other node */ +#define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) /* Allocator intends to dirty page */ /* * This may seem redundant, but it's a way of annotating false positives vs. @@ -92,7 +94,7 @@ struct vm_area_struct; */ #define __GFP_NOTRACK_FALSE_POSITIVE (__GFP_NOTRACK) -#define __GFP_BITS_SHIFT 24 /* Room for N __GFP_FOO bits */ +#define __GFP_BITS_SHIFT 25 /* Room for N __GFP_FOO bits */ #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) /* This equals 0, but use constants in case they ever change */ diff --git a/include/linux/writeback.h b/include/linux/writeback.h index 34a005515fef..6dff47304971 100644 --- a/include/linux/writeback.h +++ b/include/linux/writeback.h @@ -124,6 +124,7 @@ void laptop_mode_timer_fn(unsigned long data); static inline void laptop_sync_completion(void) { } #endif void throttle_vm_writeout(gfp_t gfp_mask); +bool zone_dirty_ok(struct zone *zone); extern unsigned long global_dirty_limit; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 433fa990fe8b..5cdd4f2b0c9d 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -147,6 +147,24 @@ static struct prop_descriptor vm_completions; * clamping level. */ +/* + * In a memory zone, there is a certain amount of pages we consider + * available for the page cache, which is essentially the number of + * free and reclaimable pages, minus some zone reserves to protect + * lowmem and the ability to uphold the zone's watermarks without + * requiring writeback. + * + * This number of dirtyable pages is the base value of which the + * user-configurable dirty ratio is the effictive number of pages that + * are allowed to be actually dirtied. Per individual zone, or + * globally by using the sum of dirtyable pages over all zones. + * + * Because the user is allowed to specify the dirty limit globally as + * absolute number of bytes, calculating the per-zone dirty limit can + * require translating the configured limit into a percentage of + * global dirtyable memory first. + */ + static unsigned long highmem_dirtyable_memory(unsigned long total) { #ifdef CONFIG_HIGHMEM @@ -232,6 +250,70 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) trace_global_dirty_state(background, dirty); } +/** + * zone_dirtyable_memory - number of dirtyable pages in a zone + * @zone: the zone + * + * Returns the zone's number of pages potentially available for dirty + * page cache. This is the base value for the per-zone dirty limits. + */ +static unsigned long zone_dirtyable_memory(struct zone *zone) +{ + /* + * The effective global number of dirtyable pages may exclude + * highmem as a big-picture measure to keep the ratio between + * dirty memory and lowmem reasonable. + * + * But this function is purely about the individual zone and a + * highmem zone can hold its share of dirty pages, so we don't + * care about vm_highmem_is_dirtyable here. + */ + return zone_page_state(zone, NR_FREE_PAGES) + + zone_reclaimable_pages(zone) - + zone->dirty_balance_reserve; +} + +/** + * zone_dirty_limit - maximum number of dirty pages allowed in a zone + * @zone: the zone + * + * Returns the maximum number of dirty pages allowed in a zone, based + * on the zone's dirtyable memory. + */ +static unsigned long zone_dirty_limit(struct zone *zone) +{ + unsigned long zone_memory = zone_dirtyable_memory(zone); + struct task_struct *tsk = current; + unsigned long dirty; + + if (vm_dirty_bytes) + dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE) * + zone_memory / global_dirtyable_memory(); + else + dirty = vm_dirty_ratio * zone_memory / 100; + + if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) + dirty += dirty / 4; + + return dirty; +} + +/** + * zone_dirty_ok - tells whether a zone is within its dirty limits + * @zone: the zone to check + * + * Returns %true when the dirty pages in @zone are within the zone's + * dirty limit, %false if the limit is exceeded. + */ +bool zone_dirty_ok(struct zone *zone) +{ + unsigned long limit = zone_dirty_limit(zone); + + return zone_page_state(zone, NR_FILE_DIRTY) + + zone_page_state(zone, NR_UNSTABLE_NFS) + + zone_page_state(zone, NR_WRITEBACK) <= limit; +} + /* * couple the period to the dirty_ratio: * diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2cb9eb71e282..4f95bcf0f2b1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1735,6 +1735,35 @@ zonelist_scan: if ((alloc_flags & ALLOC_CPUSET) && !cpuset_zone_allowed_softwall(zone, gfp_mask)) continue; + /* + * When allocating a page cache page for writing, we + * want to get it from a zone that is within its dirty + * limit, such that no single zone holds more than its + * proportional share of globally allowed dirty pages. + * The dirty limits take into account the zone's + * lowmem reserves and high watermark so that kswapd + * should be able to balance it without having to + * write pages from its LRU list. + * + * This may look like it could increase pressure on + * lower zones by failing allocations in higher zones + * before they are full. But the pages that do spill + * over are limited as the lower zones are protected + * by this very same mechanism. It should not become + * a practical burden to them. + * + * XXX: For now, allow allocations to potentially + * exceed the per-zone dirty limit in the slowpath + * (ALLOC_WMARK_LOW unset) before going into reclaim, + * which is important when on a NUMA setup the allowed + * zones are together not big enough to reach the + * global limit. The proper fix for these situations + * will require awareness of zones in the + * dirty-throttling and the flusher threads. + */ + if ((alloc_flags & ALLOC_WMARK_LOW) && + (gfp_mask & __GFP_WRITE) && !zone_dirty_ok(zone)) + goto this_zone_full; BUILD_BUG_ON(ALLOC_NO_WATERMARKS < NR_WMARK); if (!(alloc_flags & ALLOC_NO_WATERMARKS)) { |