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>

2 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 486c3972c0be..ced92345c963 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -80,6 +80,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
                 NR_TLB_LOCAL_FLUSH_ALL,
                 NR_TLB_LOCAL_FLUSH_ONE,
 #endif /* CONFIG_DEBUG_TLBFLUSH */
+#ifdef CONFIG_DEBUG_VM_VMACACHE
+                VMACACHE_FIND_CALLS,
+                VMACACHE_FIND_HITS,
+#endif
                 NR_VM_EVENT_ITEMS
 };
 
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 45c9cd1daf7a..82e7db7f7100 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -95,6 +95,12 @@ static inline void vm_events_fold_cpu(int cpu)
 #define count_vm_tlb_events(x, y) do { (void)(y); } while (0)
 #endif
 
+#ifdef CONFIG_DEBUG_VM_VMACACHE
+#define count_vm_vmacache_event(x) count_vm_event(x)
+#else
+#define count_vm_vmacache_event(x) do {} while (0)
+#endif
+
 #define __count_zone_vm_events(item, zone, delta) \
                 __count_vm_events(item##_NORMAL - ZONE_NORMAL + \
                 zone_idx(zone), delta)