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authorMikulas Patocka <mpatocka@redhat.com>2013-08-16 16:54:23 +0200
committerMike Snitzer <snitzer@redhat.com>2013-09-06 02:46:06 +0200
commitfd2ed4d252701d3bbed4cd3e3d267ad469bb832a (patch)
tree264ff043406894bd447eb6e9976b9a2b4d69bd9f /Documentation/IRQ-affinity.txt
parentdm thin: always return -ENOSPC if no_free_space is set (diff)
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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>
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