mm: treat indirectly reclaimable memory as available in MemAvailable

Adjust /proc/meminfo MemAvailable calculation by adding the amount of
indirectly reclaimable memory (rounded to the PAGE_SIZE).

Link: http://lkml.kernel.org/r/20180305133743.12746-4-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0b97b8ece4a9..b04667848375 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4734,6 +4734,13 @@ long si_mem_available(void)
                      min(global_node_page_state(NR_SLAB_RECLAIMABLE) / 2,
                          wmark_low);
 
+        /*
+         * Part of the kernel memory, which can be released under memory
+         * pressure.
+         */
+        available += global_node_page_state(NR_INDIRECTLY_RECLAIMABLE_BYTES) >>
+                PAGE_SHIFT;
+
         if (available < 0)
                 available = 0;
         return available;