05545c92db
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>
3.3 KiB
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: