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, 77 insertions, 0 deletions

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index b2c33bd955fa..36851f7f13da 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -179,6 +179,83 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_end_template, mm_vmscan_memcg_softlimit_re
         TP_ARGS(nr_reclaimed)
 );
 
+TRACE_EVENT(mm_shrink_slab_start,
+        TP_PROTO(struct shrinker *shr, struct shrink_control *sc,
+                long nr_objects_to_shrink, unsigned long pgs_scanned,
+                unsigned long lru_pgs, unsigned long cache_items,
+                unsigned long long delta, unsigned long total_scan),
+
+        TP_ARGS(shr, sc, nr_objects_to_shrink, pgs_scanned, lru_pgs,
+                cache_items, delta, total_scan),
+
+        TP_STRUCT__entry(
+                __field(struct shrinker *, shr)
+                __field(void *, shrink)
+                __field(long, nr_objects_to_shrink)
+                __field(gfp_t, gfp_flags)
+                __field(unsigned long, pgs_scanned)
+                __field(unsigned long, lru_pgs)
+                __field(unsigned long, cache_items)
+                __field(unsigned long long, delta)
+                __field(unsigned long, total_scan)
+        ),
+
+        TP_fast_assign(
+                __entry->shr = shr;
+                __entry->shrink = shr->shrink;
+                __entry->nr_objects_to_shrink = nr_objects_to_shrink;
+                __entry->gfp_flags = sc->gfp_mask;
+                __entry->pgs_scanned = pgs_scanned;
+                __entry->lru_pgs = lru_pgs;
+                __entry->cache_items = cache_items;
+                __entry->delta = delta;
+                __entry->total_scan = total_scan;
+        ),
+
+        TP_printk("%pF %p: objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
+                __entry->shrink,
+                __entry->shr,
+                __entry->nr_objects_to_shrink,
+                show_gfp_flags(__entry->gfp_flags),
+                __entry->pgs_scanned,
+                __entry->lru_pgs,
+                __entry->cache_items,
+                __entry->delta,
+                __entry->total_scan)
+);
+
+TRACE_EVENT(mm_shrink_slab_end,
+        TP_PROTO(struct shrinker *shr, int shrinker_retval,
+                long unused_scan_cnt, long new_scan_cnt),
+
+        TP_ARGS(shr, shrinker_retval, unused_scan_cnt, new_scan_cnt),
+
+        TP_STRUCT__entry(
+                __field(struct shrinker *, shr)
+                __field(void *, shrink)
+                __field(long, unused_scan)
+                __field(long, new_scan)
+                __field(int, retval)
+                __field(long, total_scan)
+        ),
+
+        TP_fast_assign(
+                __entry->shr = shr;
+                __entry->shrink = shr->shrink;
+                __entry->unused_scan = unused_scan_cnt;
+                __entry->new_scan = new_scan_cnt;
+                __entry->retval = shrinker_retval;
+                __entry->total_scan = new_scan_cnt - unused_scan_cnt;
+        ),
+
+        TP_printk("%pF %p: unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
+                __entry->shrink,
+                __entry->shr,
+                __entry->unused_scan,
+                __entry->new_scan,
+                __entry->total_scan,
+                __entry->retval)
+);
 
 DECLARE_EVENT_CLASS(mm_vmscan_lru_isolate_template,