vmscan: add shrink_slab tracepoints

It is impossible to understand what the shrinkers are actually doing
without instrumenting the code, so add a some tracepoints to allow
insight to be gained.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 7 insertions, 1 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d036e59d302b..255226554a3d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -250,6 +250,7 @@ unsigned long shrink_slab(struct shrink_control *shrink,
                 unsigned long long delta;
                 unsigned long total_scan;
                 unsigned long max_pass;
+                int shrink_ret = 0;
 
                 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
                 delta = (4 * nr_pages_scanned) / shrinker->seeks;
@@ -274,9 +275,12 @@ unsigned long shrink_slab(struct shrink_control *shrink,
                 total_scan = shrinker->nr;
                 shrinker->nr = 0;
 
+                trace_mm_shrink_slab_start(shrinker, shrink, total_scan,
+                                        nr_pages_scanned, lru_pages,
+                                        max_pass, delta, total_scan);
+
                 while (total_scan >= SHRINK_BATCH) {
                         long this_scan = SHRINK_BATCH;
-                        int shrink_ret;
                         int nr_before;
 
                         nr_before = do_shrinker_shrink(shrinker, shrink, 0);
@@ -293,6 +297,8 @@ unsigned long shrink_slab(struct shrink_control *shrink,
                 }
 
                 shrinker->nr += total_scan;
+                trace_mm_shrink_slab_end(shrinker, shrink_ret, total_scan,
+                                         shrinker->nr);
         }
         up_read(&shrinker_rwsem);
 out: