linux/Documentation/device-mapper
Mikulas Patocka fd2ed4d252 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>
2013-09-05 20:46:06 -04:00
..
cache-policies.txt dm cache: add cleaner policy 2013-03-01 22:45:52 +00:00
cache.txt dm cache: add data block size limits to code and Documentation 2013-08-23 09:02:13 -04:00
delay.txt
dm-crypt.txt
dm-flakey.txt
dm-io.txt
dm-log.txt
dm-queue-length.txt
dm-raid.txt MD: Remember the last sync operation that was performed 2013-06-26 12:38:24 +10:00
dm-service-time.txt
dm-uevent.txt
kcopyd.txt
linear.txt
persistent-data.txt
snapshot.txt
statistics.txt dm: add statistics support 2013-09-05 20:46:06 -04:00
striped.txt
switch.txt dm: add switch target 2013-07-10 23:41:19 +01:00
thin-provisioning.txt dm thin: add data block size limits to Documentation 2013-08-23 09:02:14 -04:00
verity.txt
zero.txt