diff options
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 25a75da53c27..941b802e11ec 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3713,6 +3713,49 @@ static inline void show_node(struct zone *zone) printk("Node %d ", zone_to_nid(zone)); } +long si_mem_available(void) +{ + long available; + unsigned long pagecache; + unsigned long wmark_low = 0; + unsigned long pages[NR_LRU_LISTS]; + struct zone *zone; + int lru; + + for (lru = LRU_BASE; lru < NR_LRU_LISTS; lru++) + pages[lru] = global_page_state(NR_LRU_BASE + lru); + + for_each_zone(zone) + wmark_low += zone->watermark[WMARK_LOW]; + + /* + * Estimate the amount of memory available for userspace allocations, + * without causing swapping. + */ + available = global_page_state(NR_FREE_PAGES) - totalreserve_pages; + + /* + * Not all the page cache can be freed, otherwise the system will + * start swapping. Assume at least half of the page cache, or the + * low watermark worth of cache, needs to stay. + */ + pagecache = pages[LRU_ACTIVE_FILE] + pages[LRU_INACTIVE_FILE]; + pagecache -= min(pagecache / 2, wmark_low); + available += pagecache; + + /* + * Part of the reclaimable slab consists of items that are in use, + * and cannot be freed. Cap this estimate at the low watermark. + */ + available += global_page_state(NR_SLAB_RECLAIMABLE) - + min(global_page_state(NR_SLAB_RECLAIMABLE) / 2, wmark_low); + + if (available < 0) + available = 0; + return available; +} +EXPORT_SYMBOL_GPL(si_mem_available); + void si_meminfo(struct sysinfo *val) { val->totalram = totalram_pages; |