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authorMikulas Patocka <mpatocka@redhat.com>2013-08-16 10:54:23 -0400
committerMike Snitzer <snitzer@redhat.com>2013-09-05 20:46:06 -0400
commitfd2ed4d252701d3bbed4cd3e3d267ad469bb832a (patch)
tree264ff043406894bd447eb6e9976b9a2b4d69bd9f /drivers/md/dm-ioctl.c
parent94563badaf41f9291ff0bad94a443a4319b9e312 (diff)
downloadlwn-fd2ed4d252701d3bbed4cd3e3d267ad469bb832a.tar.gz
lwn-fd2ed4d252701d3bbed4cd3e3d267ad469bb832a.zip
dm: add statistics support
Support the collection of I/O statistics on user-defined regions of a DM device. If no regions are defined no statistics are collected so there isn't any performance impact. Only bio-based DM devices are currently supported. Each user-defined region specifies a starting sector, length and step. Individual statistics will be collected for each step-sized area within the range specified. The I/O statistics counters for each step-sized area of a region are in the same format as /sys/block/*/stat or /proc/diskstats but extra counters (12 and 13) are provided: total time spent reading and writing in milliseconds. All these counters may be accessed by sending the @stats_print message to the appropriate DM device via dmsetup. The creation of DM statistics will allocate memory via kmalloc or fallback to using vmalloc space. At most, 1/4 of the overall system memory may be allocated by DM statistics. The admin can see how much memory is used by reading /sys/module/dm_mod/parameters/stats_current_allocated_bytes See Documentation/device-mapper/statistics.txt for more details. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-ioctl.c')
-rw-r--r--drivers/md/dm-ioctl.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index e9c0de75010e..afe08146f73e 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1455,20 +1455,26 @@ static int table_status(struct dm_ioctl *param, size_t param_size)
return 0;
}
-static bool buffer_test_overflow(char *result, unsigned maxlen)
-{
- return !maxlen || strlen(result) + 1 >= maxlen;
-}
-
/*
- * Process device-mapper dependent messages.
+ * Process device-mapper dependent messages. Messages prefixed with '@'
+ * are processed by the DM core. All others are delivered to the target.
* Returns a number <= 1 if message was processed by device mapper.
* Returns 2 if message should be delivered to the target.
*/
static int message_for_md(struct mapped_device *md, unsigned argc, char **argv,
char *result, unsigned maxlen)
{
- return 2;
+ int r;
+
+ if (**argv != '@')
+ return 2; /* no '@' prefix, deliver to target */
+
+ r = dm_stats_message(md, argc, argv, result, maxlen);
+ if (r < 2)
+ return r;
+
+ DMERR("Unsupported message sent to DM core: %s", argv[0]);
+ return -EINVAL;
}
/*
@@ -1542,7 +1548,7 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
if (r == 1) {
param->flags |= DM_DATA_OUT_FLAG;
- if (buffer_test_overflow(result, maxlen))
+ if (dm_message_test_buffer_overflow(result, maxlen))
param->flags |= DM_BUFFER_FULL_FLAG;
else
param->data_size = param->data_start + strlen(result) + 1;