ceph: add metadata perf metric support

Add a new "r_ended" field to struct ceph_mds_request and use that to
maintain the average latency of MDS requests.

URL: https://tracker.ceph.com/issues/43215
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/debugfs.c

@@ -171,6 +171,16 @@ static int metric_show(struct seq_file *s, void *p)
 	spin_unlock(&m->write_latency_lock);
 	CEPH_METRIC_SHOW("write", total, avg, min, max, sq);
 
+	spin_lock(&m->metadata_latency_lock);
+	total = m->total_metadatas;
+	sum = m->metadata_latency_sum;
+	avg = total > 0 ? DIV64_U64_ROUND_CLOSEST(sum, total) : 0;
+	min = m->metadata_latency_min;
+	max = m->metadata_latency_max;
+	sq = m->metadata_latency_sq_sum;
+	spin_unlock(&m->metadata_latency_lock);
+	CEPH_METRIC_SHOW("metadata", total, avg, min, max, sq);
+
 	seq_printf(s, "\n");
 	seq_printf(s, "item          total           miss            hit\n");
 	seq_printf(s, "-------------------------------------------------\n");

fs/ceph/mds_client.c

@@ -10,6 +10,7 @@
 #include <linux/seq_file.h>
 #include <linux/ratelimit.h>
 #include <linux/bits.h>
+#include <linux/ktime.h>
 
 #include "super.h"
 #include "mds_client.h"
@@ -2201,6 +2202,7 @@ ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
 	mutex_init(&req->r_fill_mutex);
 	req->r_mdsc = mdsc;
 	req->r_started = jiffies;
+	req->r_start_latency = ktime_get();
 	req->r_resend_mds = -1;
 	INIT_LIST_HEAD(&req->r_unsafe_dir_item);
 	INIT_LIST_HEAD(&req->r_unsafe_target_item);
@@ -2547,6 +2549,8 @@ out:
 static void complete_request(struct ceph_mds_client *mdsc,
 			     struct ceph_mds_request *req)
 {
+	req->r_end_latency = ktime_get();
+
 	if (req->r_callback)
 		req->r_callback(mdsc, req);
 	complete_all(&req->r_completion);
@@ -3155,6 +3159,9 @@ out_err:
 
 	/* kick calling process */
 	complete_request(mdsc, req);
+
+	ceph_update_metadata_latency(&mdsc->metric, req->r_start_latency,
+				     req->r_end_latency, err);
 out:
 	ceph_mdsc_put_request(req);
 	return;

fs/ceph/mds_client.h

@@ -10,6 +10,7 @@
 #include <linux/spinlock.h>
 #include <linux/refcount.h>
 #include <linux/utsname.h>
+#include <linux/ktime.h>
 
 #include <linux/ceph/types.h>
 #include <linux/ceph/messenger.h>
@@ -299,6 +300,8 @@ struct ceph_mds_request {
 
 	unsigned long r_timeout;  /* optional.  jiffies, 0 is "wait forever" */
 	unsigned long r_started;  /* start time to measure timeout against */
+	unsigned long r_start_latency;  /* start time to measure latency */
+	unsigned long r_end_latency;    /* finish time to measure latency */
 	unsigned long r_request_started; /* start time for mds request only,
 					    used to measure lease durations */
 

fs/ceph/metric.c

@@ -44,6 +44,13 @@ int ceph_metric_init(struct ceph_client_metric *m)
 	m->total_writes = 0;
 	m->write_latency_sum = 0;
 
+	spin_lock_init(&m->metadata_latency_lock);
+	m->metadata_latency_sq_sum = 0;
+	m->metadata_latency_min = KTIME_MAX;
+	m->metadata_latency_max = 0;
+	m->total_metadatas = 0;
+	m->metadata_latency_sum = 0;
+
 	return 0;
 
 err_i_caps_mis:
@@ -123,3 +130,19 @@ void ceph_update_write_latency(struct ceph_client_metric *m,
 			 &m->write_latency_sq_sum, lat);
 	spin_unlock(&m->write_latency_lock);
 }
+
+void ceph_update_metadata_latency(struct ceph_client_metric *m,
+				  ktime_t r_start, ktime_t r_end,
+				  int rc)
+{
+	ktime_t lat = ktime_sub(r_end, r_start);
+
+	if (unlikely(rc && rc != -ENOENT))
+		return;
+
+	spin_lock(&m->metadata_latency_lock);
+	__update_latency(&m->total_metadatas, &m->metadata_latency_sum,
+			 &m->metadata_latency_min, &m->metadata_latency_max,
+			 &m->metadata_latency_sq_sum, lat);
+	spin_unlock(&m->metadata_latency_lock);
+}

fs/ceph/metric.h

@@ -28,6 +28,13 @@ struct ceph_client_metric {
 	ktime_t write_latency_sq_sum;
 	ktime_t write_latency_min;
 	ktime_t write_latency_max;
+
+	spinlock_t metadata_latency_lock;
+	u64 total_metadatas;
+	ktime_t metadata_latency_sum;
+	ktime_t metadata_latency_sq_sum;
+	ktime_t metadata_latency_min;
+	ktime_t metadata_latency_max;
 };
 
 extern int ceph_metric_init(struct ceph_client_metric *m);
@@ -49,4 +56,7 @@ extern void ceph_update_read_latency(struct ceph_client_metric *m,
 extern void ceph_update_write_latency(struct ceph_client_metric *m,
 				      ktime_t r_start, ktime_t r_end,
 				      int rc);
+extern void ceph_update_metadata_latency(struct ceph_client_metric *m,
+				         ktime_t r_start, ktime_t r_end,
+					 int rc);
 #endif /* _FS_CEPH_MDS_METRIC_H */