[PATCH] mm: rss = file_rss + anon_rss

I was lazy when we added anon_rss, and chose to change as few places as
possible.  So currently each anonymous page has to be counted twice, in rss
and in anon_rss.  Which won't be so good if those are atomic counts in some
configurations.

Change that around: keep file_rss and anon_rss separately, and add them
together (with get_mm_rss macro) when the total is needed - reading two
atomics is much cheaper than updating two atomics.  And update anon_rss
upfront, typically in memory.c, not tucked away in page_add_anon_rmap.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 27519df0f987..afcaac66cbd5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -254,6 +254,8 @@ extern void arch_unmap_area_topdown(struct mm_struct *, unsigned long);
 #define add_mm_counter(mm, member, value) (mm)->_##member += (value)
 #define inc_mm_counter(mm, member) (mm)->_##member++
 #define dec_mm_counter(mm, member) (mm)->_##member--
+#define get_mm_rss(mm) ((mm)->_file_rss + (mm)->_anon_rss)
+
 typedef unsigned long mm_counter_t;
 
 struct mm_struct {
@@ -286,7 +288,7 @@ struct mm_struct {
         unsigned long exec_vm, stack_vm, reserved_vm, def_flags, nr_ptes;
 
         /* Special counters protected by the page_table_lock */
-        mm_counter_t _rss;
+        mm_counter_t _file_rss;
         mm_counter_t _anon_rss;
 
         unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */