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-rw-r--r--mm/page_alloc.c43
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;