mm, mmzone: clarify the usage of zone padding
Zone padding separates write-intensive fields used by page allocation,
compaction and vmstats but the comments are a little misleading and need
clarification.
Link: http://lkml.kernel.org/r/1467970510-21195-5-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
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 d4f5cac..edafdaf 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -477,20 +477,21 @@
unsigned long wait_table_hash_nr_entries;
unsigned long wait_table_bits;
+ /* Write-intensive fields used from the page allocator */
ZONE_PADDING(_pad1_)
+
/* free areas of different sizes */
struct free_area free_area[MAX_ORDER];
/* zone flags, see below */
unsigned long flags;
- /* Write-intensive fields used from the page allocator */
+ /* Primarily protects free_area */
spinlock_t lock;
+ /* Write-intensive fields used by compaction and vmstats. */
ZONE_PADDING(_pad2_)
- /* Write-intensive fields used by page reclaim */
-
/*
* When free pages are below this point, additional steps are taken
* when reading the number of free pages to avoid per-cpu counter