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, 2 deletions

diff --git a/mm/vmacache.c b/mm/vmacache.c
index 1037a3bab505..658ed3b3e38d 100644
--- a/mm/vmacache.c
+++ b/mm/vmacache.c
@@ -78,6 +78,8 @@ struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
         if (!vmacache_valid(mm))
                 return NULL;
 
+        count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
         for (i = 0; i < VMACACHE_SIZE; i++) {
                 struct vm_area_struct *vma = current->vmacache[i];
 
@@ -85,8 +87,10 @@ struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
                         continue;
                 if (WARN_ON_ONCE(vma->vm_mm != mm))
                         break;
-                if (vma->vm_start <= addr && vma->vm_end > addr)
+                if (vma->vm_start <= addr && vma->vm_end > addr) {
+                        count_vm_vmacache_event(VMACACHE_FIND_HITS);
                         return vma;
+                }
         }
 
         return NULL;
@@ -102,11 +106,15 @@ struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
         if (!vmacache_valid(mm))
                 return NULL;
 
+        count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
         for (i = 0; i < VMACACHE_SIZE; i++) {
                 struct vm_area_struct *vma = current->vmacache[i];
 
-                if (vma && vma->vm_start == start && vma->vm_end == end)
+                if (vma && vma->vm_start == start && vma->vm_end == end) {
+                        count_vm_vmacache_event(VMACACHE_FIND_HITS);
                         return vma;
+                }
         }
 
         return NULL;