linux-sg2042/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: delay target 2007-05-09 12:30:47 -07:00
dm-crypt.txt dm crypt: optionally support discard requests 2011-08-02 12:32:08 +01:00
dm-flakey.txt dm flakey: add corrupt_bio_byte feature 2011-08-02 12:32:06 +01:00
dm-io.txt
dm-log.txt dm log userspace: fix comment hyphens 2011-10-31 20:21:22 +00:00
dm-queue-length.txt dm mpath: add queue length load balancer 2009-06-22 10:12:27 +01:00
dm-raid.txt MD: Remember the last sync operation that was performed 2013-06-26 12:38:24 +10:00
dm-service-time.txt Fix common misspellings 2011-03-31 11:26:23 -03:00
dm-uevent.txt dm: uevent generate events 2007-10-20 02:01:26 +01:00
kcopyd.txt
linear.txt
persistent-data.txt Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
snapshot.txt dm: document when snapshot has finished merging 2010-03-06 02:29:56 +00:00
statistics.txt dm: add statistics support 2013-09-05 20:46:06 -04:00
striped.txt dm stripe: support for non power of 2 chunksize 2012-07-27 15:08:01 +01:00
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 dm: verity fix documentation 2012-07-03 12:55:41 +01:00
zero.txt