[PATCH 0/3] xen-blkback: do some I/O statistics rework

[PATCH 0/3] xen-blkback: do some I/O statistics rework

[Juergen Gross]

Some rework of the blkback statics data handling.

Juergen Gross (3):
  xen-blkback: Remove statistics logging on console
  xen-blkback: move statistics data into sub-structure
  xen-blkback: make statistics data persistent across disconnect/connect

 drivers/block/xen-blkback/blkback.c | 39 ++++++-----------------------
 drivers/block/xen-blkback/common.h  | 22 ++++++++++------
 drivers/block/xen-blkback/xenbus.c  | 22 ++++++++++++----
 3 files changed, 38 insertions(+), 45 deletions(-)

-- 
2.56.0

[PATCH 1/3] xen-blkback: Remove statistics logging on console

[Juergen Gross]

The xen-blkback can print I/O statistics data to the console every
10 seconds. This functionality has been present since the introduction
of xen-blkback, but retrieving the data is possible via sysfs, too.

So remove the console logging, as there is no need to have the same
functionality twice.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/block/xen-blkback/blkback.c | 25 -------------------------
 drivers/block/xen-blkback/common.h  |  1 -
 drivers/block/xen-blkback/xenbus.c  |  1 -
 3 files changed, 27 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 88526e349ce1..f3a8f3eae86b 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -126,10 +126,6 @@ MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the
  */
 #define LRU_PERCENT_CLEAN 5
 
-/* Run-time switchable: /sys/module/blkback/parameters/ */
-static unsigned int log_stats;
-module_param(log_stats, int, 0644);
-
 #define BLKBACK_INVALID_HANDLE (~0)
 
 static inline bool persistent_gnt_timeout(struct persistent_gnt *persistent_gnt)
@@ -536,21 +532,6 @@ irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
  * SCHEDULER FUNCTIONS
  */
 
-static void print_stats(struct xen_blkif_ring *ring)
-{
-	pr_info("(%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
-		 "  |  ds %4llu | pg: %4u/%4d\n",
-		 current->comm, ring->st_oo_req,
-		 ring->st_rd_req, ring->st_wr_req,
-		 ring->st_f_req, ring->st_ds_req,
-		 ring->persistent_gnt_c, max_pgrants);
-	ring->st_print = jiffies + secs_to_jiffies(10);
-	ring->st_rd_req = 0;
-	ring->st_wr_req = 0;
-	ring->st_oo_req = 0;
-	ring->st_ds_req = 0;
-}
-
 int xen_blkif_schedule(void *arg)
 {
 	struct xen_blkif_ring *ring = arg;
@@ -614,17 +595,11 @@ int xen_blkif_schedule(void *arg)
 		else
 			gnttab_page_cache_shrink(&ring->free_pages,
 						 max_buffer_pages);
-
-		if (log_stats && time_after(jiffies, ring->st_print))
-			print_stats(ring);
 	}
 
 	/* Drain pending purge work */
 	flush_work(&ring->persistent_purge_work);
 
-	if (log_stats)
-		print_stats(ring);
-
 	ring->xenblkd = NULL;
 
 	return 0;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index f5890b3f1df9..0a60e29a7cc3 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -277,7 +277,6 @@ struct xen_blkif_ring {
 	unsigned long           next_lru;
 
 	/* Statistics. */
-	unsigned long		st_print;
 	unsigned long long	st_rd_req;
 	unsigned long long	st_wr_req;
 	unsigned long long	st_oo_req;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 8d0ff8fcac22..62e3bad4ab0e 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -158,7 +158,6 @@ static int xen_blkif_alloc_rings(struct xen_blkif *blkif,
 		init_waitqueue_head(&ring->pending_free_wq);
 		init_waitqueue_head(&ring->shutdown_wq);
 		ring->blkif = blkif;
-		ring->st_print = jiffies;
 		ring->active = true;
 	}
 
-- 
2.56.0

[PATCH 2/3] xen-blkback: move statistics data into sub-structure

[Juergen Gross]

Move the statistics data into a dedicated new struct xen_blkif_stat.

This is done in preparation of not losing statistics in case of
disconnect/reconnect cycles.

No functional change intended.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/block/xen-blkback/blkback.c | 14 +++++++-------
 drivers/block/xen-blkback/common.h  | 19 ++++++++++++-------
 drivers/block/xen-blkback/xenbus.c  |  2 +-
 3 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index f3a8f3eae86b..e2f09bd4e84e 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -958,7 +958,7 @@ static int dispatch_discard_io(struct xen_blkif_ring *ring,
 			preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
 		goto fail_response;
 	}
-	ring->st_ds_req++;
+	ring->st.ds_req++;
 
 	if (blkif->vbd.discard_secure &&
 	    (req->u.discard.flag & BLKIF_DISCARD_SECURE))
@@ -1198,7 +1198,7 @@ __do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
 
 		pending_req = alloc_req(ring);
 		if (NULL == pending_req) {
-			ring->st_oo_req++;
+			ring->st.oo_req++;
 			more_to_do = 1;
 			break;
 		}
@@ -1297,11 +1297,11 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 
 	switch (req_operation) {
 	case BLKIF_OP_READ:
-		ring->st_rd_req++;
+		ring->st.rd_req++;
 		operation = REQ_OP_READ;
 		break;
 	case BLKIF_OP_WRITE:
-		ring->st_wr_req++;
+		ring->st.wr_req++;
 		operation = REQ_OP_WRITE;
 		operation_flags = REQ_SYNC | REQ_IDLE;
 		break;
@@ -1309,7 +1309,7 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 		drain = true;
 		fallthrough;
 	case BLKIF_OP_FLUSH_DISKCACHE:
-		ring->st_f_req++;
+		ring->st.f_req++;
 		operation = REQ_OP_WRITE;
 		operation_flags = REQ_PREFLUSH;
 		break;
@@ -1445,9 +1445,9 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 	blk_finish_plug(&plug);
 
 	if (operation == REQ_OP_READ)
-		ring->st_rd_sect += preq.nr_sects;
+		ring->st.rd_sect += preq.nr_sects;
 	else if (operation == REQ_OP_WRITE)
-		ring->st_wr_sect += preq.nr_sects;
+		ring->st.wr_sect += preq.nr_sects;
 
 	return 0;
 
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 0a60e29a7cc3..f8385c4b9d30 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -248,6 +248,17 @@ struct persistent_gnt {
 	struct list_head remove_node;
 };
 
+/* Statistic data. */
+struct xen_blkif_stat {
+	unsigned long long	rd_req;
+	unsigned long long	wr_req;
+	unsigned long long	oo_req;
+	unsigned long long	f_req;
+	unsigned long long	ds_req;
+	unsigned long long	rd_sect;
+	unsigned long long	wr_sect;
+};
+
 /* Per-ring information. */
 struct xen_blkif_ring {
 	/* Physical parameters of the comms window. */
@@ -277,13 +288,7 @@ struct xen_blkif_ring {
 	unsigned long           next_lru;
 
 	/* Statistics. */
-	unsigned long long	st_rd_req;
-	unsigned long long	st_wr_req;
-	unsigned long long	st_oo_req;
-	unsigned long long	st_f_req;
-	unsigned long long	st_ds_req;
-	unsigned long long	st_rd_sect;
-	unsigned long long	st_wr_sect;
+	struct xen_blkif_stat	st;
 
 	/* Used by the kworker that offload work from the persistent purge. */
 	struct list_head	persistent_purge_list;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 62e3bad4ab0e..b3ef483a92fd 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -408,7 +408,7 @@ void xen_blkif_interface_fini(void)
 		for (i = 0; i < blkif->nr_rings; i++) {		\
 			struct xen_blkif_ring *ring = &blkif->rings[i];	\
 									\
-			result += ring->st_##name;			\
+			result += ring->st.name;			\
 		}							\
 									\
 out:									\
-- 
2.56.0

[PATCH 3/3] xen-blkback: make statistics data persistent across disconnect/connect

[Juergen Gross]

Today the statistics data is living in struct xen_blkif_ring only.

This means that a disconnect/connect cycle will reset the data, as the
rings are freed and re-allocated in this case.

Add a struct xen_blkif_stat in struct xen_blkif and sum up the per-ring
data there when freeing the rings, and add those values to the printed
statistics data.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/block/xen-blkback/common.h |  2 ++
 drivers/block/xen-blkback/xenbus.c | 19 ++++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index f8385c4b9d30..c35ec207b31d 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -327,6 +327,8 @@ struct xen_blkif {
 	unsigned int		nr_rings;
 
 	unsigned long		buffer_squeeze_end;
+
+	struct xen_blkif_stat	st;
 };
 
 struct seg_buf {
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index b3ef483a92fd..f0d4cec4432a 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -346,6 +346,18 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
 	 */
 	write_lock(&blkif->rings_lock);
 
+	for (r = 0; r < blkif->nr_rings; r++) {
+		struct xen_blkif_ring *ring = &blkif->rings[r];
+
+		blkif->st.rd_req += ring->st.rd_req;
+		blkif->st.wr_req += ring->st.wr_req;
+		blkif->st.oo_req += ring->st.oo_req;
+		blkif->st.f_req += ring->st.f_req;
+		blkif->st.ds_req += ring->st.ds_req;
+		blkif->st.rd_sect += ring->st.rd_sect;
+		blkif->st.wr_sect += ring->st.wr_sect;
+	}
+
 	rings = blkif->rings;
 	blkif->rings = NULL;
 	blkif->nr_rings = 0;
@@ -399,13 +411,14 @@ void xen_blkif_interface_fini(void)
 		struct backend_info *be = dev_get_drvdata(&dev->dev);	\
 		struct xen_blkif *blkif = be->blkif;			\
 		unsigned int i;						\
-		unsigned long long result = 0;				\
+		unsigned long long result;				\
 									\
 		read_lock(&blkif->rings_lock);				\
-		if (!blkif->rings)				\
+		result = blkif->st.name;				\
+		if (!blkif->rings)					\
 			goto out;					\
 									\
-		for (i = 0; i < blkif->nr_rings; i++) {		\
+		for (i = 0; i < blkif->nr_rings; i++) {			\
 			struct xen_blkif_ring *ring = &blkif->rings[i];	\
 									\
 			result += ring->st.name;			\
-- 
2.56.0