[PATCH] mm/vmscan: expose cgroup_ino for shrink slab tracepoints

[Yafang Shao <laoar.shao@gmail.com>]

There may be many containers deployed on one host. But we only
want to trace the slab caches in a speficed container sometimes.
The exposed cgroup_ino in mm_shrink_slab_{start, end} tracepoints can
help us.

It can be used as bellow,
step 1, get the inode of the specified cgroup
	$ ls -di /tmp/cgroupv2/foo
step 2, set this inode into tracepoint filter to trace this cgroup only
	(assume the inode is 11)
	$ cd /sys/kernel/debug/tracing/events/vmscan/
	$ echo 'cgroup_ino == 11' > mm_shrink_slab_start/filter
	$ echo 'cgroup_ino == 11' > mm_shrink_slab_end/filter

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/trace/events/vmscan.h | 23 +++++++++++++++--------
 mm/vmscan.c                   |  3 ++-
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
index c37e228..4f80fa3 100644
--- a/include/trace/events/vmscan.h
+++ b/include/trace/events/vmscan.h
@@ -248,6 +248,7 @@
 		__field(unsigned long long, delta)
 		__field(unsigned long, total_scan)
 		__field(int, priority)
+		__field(unsigned int, cgroup_ino)
 	),
 
 	TP_fast_assign(
@@ -260,9 +261,10 @@
 		__entry->delta = delta;
 		__entry->total_scan = total_scan;
 		__entry->priority = priority;
+		__entry->cgroup_ino = cgroup_ino(sc->memcg->css.cgroup);
 	),
 
-	TP_printk("%pS %p: nid: %d objects to shrink %ld gfp_flags %s cache items %ld delta %lld total_scan %ld priority %d",
+	TP_printk("%pS %p: nid: %d objects to shrink %ld gfp_flags %s cache items %ld delta %lld total_scan %ld priority %d cgroup_ino %u",
 		__entry->shrink,
 		__entry->shr,
 		__entry->nid,
@@ -271,14 +273,16 @@
 		__entry->cache_items,
 		__entry->delta,
 		__entry->total_scan,
-		__entry->priority)
+		__entry->priority,
+		__entry->cgroup_ino)
 );
 
 TRACE_EVENT(mm_shrink_slab_end,
-	TP_PROTO(struct shrinker *shr, int nid, int shrinker_retval,
-		long unused_scan_cnt, long new_scan_cnt, long total_scan),
+	TP_PROTO(struct shrinker *shr, struct shrink_control *sc,
+		int shrinker_retval, long unused_scan_cnt,
+		long new_scan_cnt, long total_scan),
 
-	TP_ARGS(shr, nid, shrinker_retval, unused_scan_cnt, new_scan_cnt,
+	TP_ARGS(shr, sc, shrinker_retval, unused_scan_cnt, new_scan_cnt,
 		total_scan),
 
 	TP_STRUCT__entry(
@@ -289,26 +293,29 @@
 		__field(long, new_scan)
 		__field(int, retval)
 		__field(long, total_scan)
+		__field(unsigned int, cgroup_ino)
 	),
 
 	TP_fast_assign(
 		__entry->shr = shr;
-		__entry->nid = nid;
+		__entry->nid = sc->nid;
 		__entry->shrink = shr->scan_objects;
 		__entry->unused_scan = unused_scan_cnt;
 		__entry->new_scan = new_scan_cnt;
 		__entry->retval = shrinker_retval;
 		__entry->total_scan = total_scan;
+		__entry->cgroup_ino = cgroup_ino(sc->memcg->css.cgroup);
 	),
 
-	TP_printk("%pS %p: nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
+	TP_printk("%pS %p: nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d cgroup_ino %u",
 		__entry->shrink,
 		__entry->shr,
 		__entry->nid,
 		__entry->unused_scan,
 		__entry->new_scan,
 		__entry->total_scan,
-		__entry->retval)
+		__entry->retval,
+		__entry->cgroup_ino)
 );
 
 TRACE_EVENT(mm_vmscan_lru_isolate,
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d6c3fc8..a9a03a4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -578,7 +578,8 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 	else
 		new_nr = atomic_long_read(&shrinker->nr_deferred[nid]);
 
-	trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
+	trace_mm_shrink_slab_end(shrinker, shrinkctl, freed, nr, new_nr,
+				 total_scan);
 	return freed;
 }
 
-- 
1.8.3.1