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authorSeymour, Shane M <shane.seymour@hp.com>2015-05-06 04:37:20 +0300
committerJames Bottomley <JBottomley@Odin.com>2015-06-02 18:03:25 +0300
commit05545c92db9637318a98d3d59d400beb819decc7 (patch)
tree56c911568dd7dd6507aac24f7c8c90b657f7bda0 /Documentation/ABI/testing/sysfs-class-scsi_tape
parentba929992522b6d1f866b7021bc50da66f8fdd743 (diff)
downloadlinux-05545c92db9637318a98d3d59d400beb819decc7.tar.xz
st: implement tape statistics
This patch implements tape statistics in the st module via sysfs. Current no statistics are available for tape I/O and there is no easy way to reuse the block layer statistics for tape as tape is a character device and does not have perform I/O in sector sized chunks (the size of the data written to tape can change). For tapes we also need extra stats related to things like tape movement (via other I/O). There have been multiple end users requesting statistics including AT&T (and some HP customers who have not given permission to be named). It is impossible for them to investigate any issues related to tape performance in a non-invasive way. [jejb: eliminate PRId64] Signed-off-by: Shane Seymour <shane.seymour@hp.com> Tested-by: Shane Seymour <shane.seymour@hp.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: James Bottomley <JBottomley@Odin.com>
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+What: /sys/class/scsi_tape/*/stats/in_flight
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Show the number of I/Os currently in-flight between the st
+ module and the SCSI mid-layer.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/io_ns
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total amount of time spent waiting for all I/O
+ to and from the tape drive to complete. This includes all
+ reads, writes, and other SCSI commands issued to the tape
+ drive. An example of other SCSI commands would be tape
+ movement such as a rewind when a rewind tape device is
+ closed. This item is measured in nanoseconds.
+
+ To determine the amount of time spent waiting for other I/O
+ to complete subtract read_ns and write_ns from this value.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/other_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ The number of I/O requests issued to the tape drive other
+ than SCSI read/write requests.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/read_byte_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of bytes requested from the tape drive.
+ This value is presented in bytes because tape drives support
+ variable length block sizes.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/read_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of read requests issued to the tape
+ drive.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/read_ns
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total amount of time in nanoseconds waiting for
+ read I/O requests to complete.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/write_byte_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of bytes written to the tape drive.
+ This value is presented in bytes because tape drives support
+ variable length block sizes.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/write_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total number of write requests issued to the tape
+ drive.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/write_ms
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the total amount of time in nanoseconds waiting for
+ write I/O requests to complete.
+Users:
+
+
+What: /sys/class/scsi_tape/*/stats/resid_cnt
+Date: Apr 2015
+KernelVersion: 4.2
+Contact: Shane Seymour <shane.seymour@hp.com>
+Description:
+ Shows the number of times we found that a residual >0
+ was found when the SCSI midlayer indicated that there was
+ an error. For reads this may be a case of someone issuing
+ reads greater than the block size.
+Users: