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>

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>
Dave Chinner · Al Viro
1 parent a9049376ee
Showing 2 changed files with 84 additions and 1 deletions Side-by-side Diff
include/trace/events/vmscan.h
mm/vmscan.c
@@ -179,6 +179,83 @@
 	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,
  
@@ -250,6 +250,7 @@
 		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 @@
 		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 @@
 		}
  
 		shrinker->nr += total_scan;
+		trace_mm_shrink_slab_end(shrinker, shrink_ret, total_scan,
+					 shrinker->nr);
 	}
 	up_read(&shrinker_rwsem);
 out:
...	...	@@ -179,6 +179,83 @@
179	179	TP_ARGS(nr_reclaimed)
180	180	);
181	181
	182	+TRACE_EVENT(mm_shrink_slab_start,
	183	+ TP_PROTO(struct shrinker shr, struct shrink_control sc,
	184	+ long nr_objects_to_shrink, unsigned long pgs_scanned,
	185	+ unsigned long lru_pgs, unsigned long cache_items,
	186	+ unsigned long long delta, unsigned long total_scan),
	187	+
	188	+ TP_ARGS(shr, sc, nr_objects_to_shrink, pgs_scanned, lru_pgs,
	189	+ cache_items, delta, total_scan),
	190	+
	191	+ TP_STRUCT__entry(
	192	+ __field(struct shrinker *, shr)
	193	+ __field(void *, shrink)
	194	+ __field(long, nr_objects_to_shrink)
	195	+ __field(gfp_t, gfp_flags)
	196	+ __field(unsigned long, pgs_scanned)
	197	+ __field(unsigned long, lru_pgs)
	198	+ __field(unsigned long, cache_items)
	199	+ __field(unsigned long long, delta)
	200	+ __field(unsigned long, total_scan)
	201	+ ),
	202	+
	203	+ TP_fast_assign(
	204	+ __entry->shr = shr;
	205	+ __entry->shrink = shr->shrink;
	206	+ __entry->nr_objects_to_shrink = nr_objects_to_shrink;
	207	+ __entry->gfp_flags = sc->gfp_mask;
	208	+ __entry->pgs_scanned = pgs_scanned;
	209	+ __entry->lru_pgs = lru_pgs;
	210	+ __entry->cache_items = cache_items;
	211	+ __entry->delta = delta;
	212	+ __entry->total_scan = total_scan;
	213	+ ),
	214	+
	215	+ 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",
	216	+ __entry->shrink,
	217	+ __entry->shr,
	218	+ __entry->nr_objects_to_shrink,
	219	+ show_gfp_flags(__entry->gfp_flags),
	220	+ __entry->pgs_scanned,
	221	+ __entry->lru_pgs,
	222	+ __entry->cache_items,
	223	+ __entry->delta,
	224	+ __entry->total_scan)
	225	+);
	226	+
	227	+TRACE_EVENT(mm_shrink_slab_end,
	228	+ TP_PROTO(struct shrinker *shr, int shrinker_retval,
	229	+ long unused_scan_cnt, long new_scan_cnt),
	230	+
	231	+ TP_ARGS(shr, shrinker_retval, unused_scan_cnt, new_scan_cnt),
	232	+
	233	+ TP_STRUCT__entry(
	234	+ __field(struct shrinker *, shr)
	235	+ __field(void *, shrink)
	236	+ __field(long, unused_scan)
	237	+ __field(long, new_scan)
	238	+ __field(int, retval)
	239	+ __field(long, total_scan)
	240	+ ),
	241	+
	242	+ TP_fast_assign(
	243	+ __entry->shr = shr;
	244	+ __entry->shrink = shr->shrink;
	245	+ __entry->unused_scan = unused_scan_cnt;
	246	+ __entry->new_scan = new_scan_cnt;
	247	+ __entry->retval = shrinker_retval;
	248	+ __entry->total_scan = new_scan_cnt - unused_scan_cnt;
	249	+ ),
	250	+
	251	+ TP_printk("%pF %p: unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
	252	+ __entry->shrink,
	253	+ __entry->shr,
	254	+ __entry->unused_scan,
	255	+ __entry->new_scan,
	256	+ __entry->total_scan,
	257	+ __entry->retval)
	258	+);
182	259
183	260	DECLARE_EVENT_CLASS(mm_vmscan_lru_isolate_template,
184	261
...	...	@@ -250,6 +250,7 @@
250	250	unsigned long long delta;
251	251	unsigned long total_scan;
252	252	unsigned long max_pass;
	253	+ int shrink_ret = 0;
253	254
254	255	max_pass = do_shrinker_shrink(shrinker, shrink, 0);
255	256	delta = (4 * nr_pages_scanned) / shrinker->seeks;
256	257
...	...	@@ -274,9 +275,12 @@
274	275	total_scan = shrinker->nr;
275	276	shrinker->nr = 0;
276	277
	278	+ trace_mm_shrink_slab_start(shrinker, shrink, total_scan,
	279	+ nr_pages_scanned, lru_pages,
	280	+ max_pass, delta, total_scan);
	281	+
277	282	while (total_scan >= SHRINK_BATCH) {
278	283	long this_scan = SHRINK_BATCH;
279		- int shrink_ret;
280	284	int nr_before;
281	285
282	286	nr_before = do_shrinker_shrink(shrinker, shrink, 0);
...	...	@@ -293,6 +297,8 @@
293	297	}
294	298
295	299	shrinker->nr += total_scan;
	300	+ trace_mm_shrink_slab_end(shrinker, shrink_ret, total_scan,
	301	+ shrinker->nr);
296	302	}
297	303	up_read(&shrinker_rwsem);
298	304	out: