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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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.. | ||
cache-policies.txt | ||
cache.txt | ||
delay.txt | ||
dm-crypt.txt | ||
dm-flakey.txt | ||
dm-io.txt | ||
dm-log.txt | ||
dm-queue-length.txt | ||
dm-raid.txt | ||
dm-service-time.txt | ||
dm-uevent.txt | ||
kcopyd.txt | ||
linear.txt | ||
persistent-data.txt | ||
snapshot.txt | ||
statistics.txt | ||
striped.txt | ||
switch.txt | ||
thin-provisioning.txt | ||
verity.txt | ||
zero.txt |