mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES

Patch series "indirectly reclaimable memory", v2.

This patchset introduces the concept of indirectly reclaimable memory
and applies it to fix the issue of when a big number of dentries with
external names can significantly affect the MemAvailable value.

This patch (of 3):

Introduce a concept of indirectly reclaimable memory and adds the
corresponding memory counter and /proc/vmstat item.

Indirectly reclaimable memory is any sort of memory, used by the kernel
(except of reclaimable slabs), which is actually reclaimable, i.e.  will
be released under memory pressure.

The counter is in bytes, as it's not always possible to count such
objects in pages.  The name contains BYTES by analogy to
NR_KERNEL_STACK_KB.

Link: http://lkml.kernel.org/r/20180305133743.12746-2-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>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index f11ae29005f1b44cfda0958235043a4e51dbd830..a0c9e45a859a7ca364cbe43adafc27710455642c 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -180,6 +180,7 @@ enum node_stat_item {
        NR_VMSCAN_IMMEDIATE,    /* Prioritise for reclaim when writeback ends */
        NR_DIRTIED,             /* page dirtyings since bootup */
        NR_WRITTEN,             /* page writings since bootup */
+       NR_INDIRECTLY_RECLAIMABLE_BYTES, /* measured in bytes */
        NR_VM_NODE_STAT_ITEMS
 };
 

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 33581be705f03ee97527ad61921c3339a05524d0..536332e988b872973b1e4dc663eebf0c3f595802 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1161,6 +1161,7 @@ const char * const vmstat_text[] = {
        "nr_vmscan_immediate_reclaim",
        "nr_dirtied",
        "nr_written",
+       "nr_indirectly_reclaimable",
 
        /* enum writeback_stat_item counters */
        "nr_dirty_threshold",