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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 | ||