mm,vmacache: add debug data

Introduce a CONFIG_DEBUG_VM_VMACACHE option to enable counting the cache
hit rate -- exported in /proc/vmstat.

Any updates to the caching scheme needs this kind of data, thus it can
save some work re-implementing the counting all the time.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 99c8bfee1b00..c2de65045a40 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -501,6 +501,16 @@ config DEBUG_VM
 
           If unsure, say N.
 
+config DEBUG_VM_VMACACHE
+        bool "Debug VMA caching"
+        depends on DEBUG_VM
+        help
+          Enable this to turn on VMA caching debug information. Doing so
+          can cause significant overhead, so only enable it in non-production
+          environments.
+
+          If unsure, say N.
+
 config DEBUG_VM_RB
         bool "Debug VM red-black trees"
         depends on DEBUG_VM