Add a few new shrinker stats.
number of objects requested to free, number of objects freed:
Shrinkers won't necessarily free all objects requested for a variety of
reasons, but if the two counts are wildly different something is likely
amiss.
.scan_objects runtime:
If one shrinker is taking an excessive amount of time to free
objects that will block kswapd from running other shrinkers.
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
---
include/linux/shrinker.h | 6 ++++++
mm/shrinker.c | 23 ++++++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 6193612617a1..106622ddac77 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -118,6 +118,12 @@ struct shrinker {
#endif
/* objs pending delete, per node */
atomic_long_t *nr_deferred;
+
+ atomic_long_t objects_requested_to_free;
+ atomic_long_t objects_freed;
+ unsigned long last_freed; /* timestamp, in jiffies */
+ unsigned long last_scanned; /* timestamp, in jiffies */
+ atomic64_t ns_run;
};
#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
diff --git a/mm/shrinker.c b/mm/shrinker.c
index ad52c269bb48..feaa8122afc9 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -430,13 +430,24 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
total_scan >= freeable) {
unsigned long ret;
unsigned long nr_to_scan = min(batch_size, total_scan);
+ u64 start_time = ktime_get_ns();
+
+ atomic_long_add(nr_to_scan, &shrinker->objects_requested_to_free);
shrinkctl->nr_to_scan = nr_to_scan;
shrinkctl->nr_scanned = nr_to_scan;
ret = shrinker->scan_objects(shrinker, shrinkctl);
+
+ atomic64_add(ktime_get_ns() - start_time, &shrinker->ns_run);
if (ret == SHRINK_STOP)
break;
freed += ret;
+ unsigned long now = jiffies;
+ if (ret) {
+ atomic_long_add(ret, &shrinker->objects_freed);
+ shrinker->last_freed = now;
+ }
+ shrinker->last_scanned = now;
count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
total_scan -= shrinkctl->nr_scanned;
@@ -812,9 +823,19 @@ EXPORT_SYMBOL_GPL(shrinker_free);
void shrinker_to_text(struct seq_buf *out, struct shrinker *shrinker)
{
struct shrink_control sc = { .gfp_mask = GFP_KERNEL, };
+ unsigned long nr_freed = atomic_long_read(&shrinker->objects_freed);
seq_buf_puts(out, shrinker->name);
- seq_buf_printf(out, " objects: %lu\n", shrinker->count_objects(shrinker, &sc));
+ seq_buf_putc(out, '\n');
+
+ seq_buf_printf(out, "objects: %lu\n", shrinker->count_objects(shrinker, &sc));
+ seq_buf_printf(out, "requested to free: %lu\n", atomic_long_read(&shrinker->objects_requested_to_free));
+ seq_buf_printf(out, "objects freed: %lu\n", nr_freed);
+ seq_buf_printf(out, "last scanned: %li sec ago\n", (jiffies - shrinker->last_scanned) / HZ);
+ seq_buf_printf(out, "last freed: %li sec ago\n", (jiffies - shrinker->last_freed) / HZ);
+ seq_buf_printf(out, "ns per object freed: %llu\n", nr_freed
+ ? div64_ul(atomic64_read(&shrinker->ns_run), nr_freed)
+ : 0);
if (shrinker->to_text) {
shrinker->to_text(out, shrinker);
--
2.45.2
