linux-toradex.git/Documentation/device-mapper/statistics.txt, branch v4.2.6

dm stats: report precise_timestamps and histogram in @stats_list output

2015-09-21T17:10:59+00:00

commit bd49784fd1e8f42c7600fbfa206361324857f373 upstream.

If the user selected the precise_timestamps or histogram options, report
it in the @stats_list message output.

If the user didn't select these options, no extra tokens are reported,
thus it is backward compatible with old software that doesn't know about
precise timestamps and histogram.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Cc: stable@vger.kernel.org # 4.2
Signed-off-by: Greg Kroah-Hartman

dm stats: collect and report histogram of IO latencies

2015-06-17T16:40:40+00:00

Add an option to dm statistics to collect and report a histogram of
IO latencies.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm stats: support precise timestamps

2015-06-17T16:40:40+00:00

Make it possible to use precise timestamps with nanosecond granularity
in dm statistics.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm: add statistics support

2013-09-06T00:46:06+00:00

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 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon