bdev: support to get histogram per channel

Added new API 'spdk_bdev_histogram_get_channel' to get histogram of
a specified channel for a bdev. A callback function is passed to it
to process the histogram.

Change-Id: If5d56cbb5fe6c39cda7882f887dcc9c6afa769ac
Signed-off-by: Richael Zhuang <richael.zhuang@arm.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/15539
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Mellanox Build Bot
Reviewed-by: Aleksey Marchuk <alexeymar@nvidia.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <smatsumoto@nvidia.com>

CHANGELOG.md

@@ -33,6 +33,9 @@ running `bdev_nvme_set_options` RPC with `--generate-uuids` option. These identi
 are based on serial number and namespace ID and will always be the same for a given
 device.
 
+A new API `spdk_bdev_channel_get_histogram` was added to get the histogram of a specified
+channel for a bdev.
+
 ### event
 
 Added core lock file mechanism to prevent the same CPU cores from being used by multiple

include/spdk/bdev.h

@@ -1938,6 +1938,19 @@ void spdk_bdev_histogram_get(struct spdk_bdev *bdev, struct spdk_histogram_data
 			     spdk_bdev_histogram_data_cb cb_fn,
 			     void *cb_arg);
 
+/**
+ * Get histogram data of the specified channel for a bdev. The histogram passed to cb_fn
+ * is only valid during the execution of cb_fn. Referencing the histogram after cb_fn
+ * returns is not supported and yields undetermined behavior.
+ *
+ * \param bdev Block device.
+ * \param ch IO channel of bdev.
+ * \param cb_fn Callback function to process the histogram of the channel.
+ * \param cb_arg Argument to pass to cb_fn.
+ */
+void spdk_bdev_channel_get_histogram(struct spdk_bdev *bdev, struct spdk_io_channel *ch,
+				     spdk_bdev_histogram_data_cb cb_fn, void *cb_arg);
+
 /**
  * Retrieves media events.  Can only be called from the context of
  * SPDK_BDEV_EVENT_MEDIA_MANAGEMENT event callback.  These events are sent by

lib/bdev/bdev.c

@@ -7634,6 +7634,21 @@ spdk_bdev_histogram_get(struct spdk_bdev *bdev, struct spdk_histogram_data *hist
 				   bdev_histogram_get_channel_cb);
 }
 
+void
+spdk_bdev_channel_get_histogram(struct spdk_bdev *bdev, struct spdk_io_channel *ch,
+				spdk_bdev_histogram_data_cb cb_fn, void *cb_arg)
+{
+	struct spdk_bdev_channel *bdev_ch = __io_ch_to_bdev_ch(ch);
+	int status = 0;
+
+	assert(cb_fn != NULL);
+
+	if (bdev_ch->histogram == NULL) {
+		status = -EFAULT;
+	}
+	cb_fn(cb_arg, status, bdev_ch->histogram);
+}
+
 size_t
 spdk_bdev_get_media_events(struct spdk_bdev_desc *desc, struct spdk_bdev_media_event *events,
 			   size_t max_events)

lib/bdev/spdk_bdev.map

@@ -99,6 +99,7 @@
 	spdk_bdev_io_get_seek_offset;
 	spdk_bdev_histogram_enable;
 	spdk_bdev_histogram_get;
+	spdk_bdev_channel_get_histogram;
 	spdk_bdev_get_media_events;
 	spdk_bdev_get_memory_domains;
 	spdk_bdev_readv_blocks_ext;

test/unit/lib/bdev/bdev.c/bdev_ut.c

@@ -3423,6 +3423,18 @@ histogram_io_count(void *ctx, uint64_t start, uint64_t end, uint64_t count,
 	g_count += count;
 }
 
+static void
+histogram_channel_data_cb(void *cb_arg, int status, struct spdk_histogram_data *histogram)
+{
+	spdk_histogram_data_fn cb_fn = cb_arg;
+
+	g_status = status;
+
+	if (status == 0) {
+		spdk_histogram_data_iterate(histogram, cb_fn, NULL);
+	}
+}
+
 static void
 bdev_histograms(void)
 {
@@ -3493,6 +3505,11 @@ bdev_histograms(void)
 	spdk_histogram_data_iterate(g_histogram, histogram_io_count, NULL);
 	CU_ASSERT(g_count == 2);
 
+	g_count = 0;
+	spdk_bdev_channel_get_histogram(bdev, ch, histogram_channel_data_cb, histogram_io_count);
+	CU_ASSERT(g_status == 0);
+	CU_ASSERT(g_count == 2);
+
 	/* Disable histogram */
 	spdk_bdev_histogram_enable(bdev, histogram_status_cb, NULL, false);
 	poll_threads();
@@ -3504,6 +3521,9 @@ bdev_histograms(void)
 	poll_threads();
 	CU_ASSERT(g_status == -EFAULT);
 
+	spdk_bdev_channel_get_histogram(bdev, ch, histogram_channel_data_cb, NULL);
+	CU_ASSERT(g_status == -EFAULT);
+
 	spdk_histogram_data_free(histogram);
 	spdk_put_io_channel(ch);
 	spdk_bdev_close(desc);