[Qemu-block] [PATCH v2 10/22] block: Add average I/O queue depth to BlockDeviceTimedStats

[Alberto Garcia]

This patch adds two new fields to BlockDeviceTimedStats that track the
average number of pending read and write requests for a block device.

The values are calculated for the period of time defined for that
interval.

Signed-off-by: Alberto Garcia <address@hidden>
---
 block/accounting.c           | 12 ++++++++++++
 block/qapi.c                 |  5 +++++
 include/block/accounting.h   |  2 ++
 include/qemu/timed-average.h |  1 +
 qapi/block-core.json         |  9 ++++++++-
 qmp-commands.hx              |  6 ++++++
 util/timed-average.c         | 17 +++++++++++++++++
 7 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/block/accounting.c b/block/accounting.c
index c74a473..d94ebed 100644
--- a/block/accounting.c
+++ b/block/accounting.c
@@ -138,3 +138,15 @@ int64_t block_acct_idle_time_ns(BlockAcctStats *stats)
 {
     return qemu_clock_get_ns(clock_type) - stats->last_access_time_ns;
 }
+
+double block_acct_queue_depth(BlockAcctTimedStats *stats,
+                              enum BlockAcctType type)
+{
+    uint64_t sum, elapsed;
+
+    assert(type < BLOCK_MAX_IOTYPE);
+
+    sum = timed_average_sum(&stats->latency[type], &elapsed);
+
+    return (double) sum / elapsed;
+}
diff --git a/block/qapi.c b/block/qapi.c
index fdddb45..2fec5e1 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -404,6 +404,11 @@ static BlockStats *bdrv_query_stats(const BlockDriverState 
*bs,
             dev_stats->min_flush_latency_ns = timed_average_min(fl);
             dev_stats->max_flush_latency_ns = timed_average_max(fl);
             dev_stats->avg_flush_latency_ns = timed_average_avg(fl);
+
+            dev_stats->avg_rd_queue_depth =
+                block_acct_queue_depth(ts, BLOCK_ACCT_READ);
+            dev_stats->avg_wr_queue_depth =
+                block_acct_queue_depth(ts, BLOCK_ACCT_WRITE);
         }
     }
 
diff --git a/include/block/accounting.h b/include/block/accounting.h
index 09605bb..f41ddde 100644
--- a/include/block/accounting.h
+++ b/include/block/accounting.h
@@ -78,5 +78,7 @@ void block_acct_invalid(BlockAcctStats *stats, enum 
BlockAcctType type);
 void block_acct_merge_done(BlockAcctStats *stats, enum BlockAcctType type,
                            int num_requests);
 int64_t block_acct_idle_time_ns(BlockAcctStats *stats);
+double block_acct_queue_depth(BlockAcctTimedStats *stats,
+                              enum BlockAcctType type);
 
 #endif
diff --git a/include/qemu/timed-average.h b/include/qemu/timed-average.h
index f1cdddc..364bf88 100644
--- a/include/qemu/timed-average.h
+++ b/include/qemu/timed-average.h
@@ -59,5 +59,6 @@ void timed_average_account(TimedAverage *ta, uint64_t value);
 uint64_t timed_average_min(TimedAverage *ta);
 uint64_t timed_average_avg(TimedAverage *ta);
 uint64_t timed_average_max(TimedAverage *ta);
+uint64_t timed_average_sum(TimedAverage *ta, uint64_t *elapsed);
 
 #endif
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 45f913b..c6db03b 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -450,6 +450,12 @@
 # @avg_flush_latency_ns: Average latency of flush operations in the
 #                        defined interval, in nanoseconds.
 #
+# @avg_rd_queue_depth: Average number of pending read operations
+#                      in the defined interval.
+#
+# @avg_wr_queue_depth: Average number of pending write operations
+#                      in the defined interval.
+#
 # Since: 2.5
 ##
 
@@ -458,7 +464,8 @@
             'max_rd_latency_ns': 'int', 'avg_rd_latency_ns': 'int',
             'min_wr_latency_ns': 'int', 'max_wr_latency_ns': 'int',
             'avg_wr_latency_ns': 'int', 'min_flush_latency_ns': 'int',
-            'max_flush_latency_ns': 'int', 'avg_flush_latency_ns': 'int' } }
+            'max_flush_latency_ns': 'int', 'avg_flush_latency_ns': 'int',
+            'avg_rd_queue_depth': 'number', 'avg_wr_queue_depth': 'number' } }
 
 ##
 # @BlockDeviceStats:
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 33f2897..533edf5 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2564,6 +2564,12 @@ Each json-object contain the following:
         - "avg_flush_latency_ns": average latency of flush operations
                                   in the defined interval, in
                                   nanoseconds (json-int)
+        - "avg_rd_queue_depth": average number of pending read
+                                operations in the defined interval
+                                (json-number)
+        - "avg_wr_queue_depth": average number of pending write
+                                operations in the defined interval
+                                (json-number).
 - "parent": Contains recursively the statistics of the underlying
             protocol (e.g. the host file for a qcow2 image). If there is
             no underlying protocol, this field is omitted
diff --git a/util/timed-average.c b/util/timed-average.c
index 1f4689e..4263b29 100644
--- a/util/timed-average.c
+++ b/util/timed-average.c
@@ -208,3 +208,20 @@ uint64_t timed_average_max(TimedAverage *ta)
     check_expirations(ta);
     return current_window(ta)->max;
 }
+
+/* Get the sum of all accounted values
+ * @ta:      the TimedAverage structure
+ * @elapsed: if non-NULL, the elapsed time (in ns) will be stored here
+ * @ret:     the sum of all accounted values
+ */
+uint64_t timed_average_sum(TimedAverage *ta, uint64_t *elapsed)
+{
+    TimedAverageWindow *w;
+    check_expirations(ta);
+    w = current_window(ta);
+    if (elapsed != NULL) {
+        int64_t remaining = w->expiration - qemu_clock_get_ns(ta->clock_type);
+        *elapsed = ta->period - remaining;
+    }
+    return w->sum;
+}
-- 
2.5.3