diff options
| -rw-r--r-- | Documentation/ABI/testing/procfs-diskstats | 22 | ||||
| -rw-r--r-- | Documentation/ABI/testing/sysfs-block | 28 | ||||
| -rw-r--r-- | Documentation/iostats.txt | 15 |
3 files changed, 64 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats new file mode 100644 index 000000000000..99233902e09e --- /dev/null +++ b/Documentation/ABI/testing/procfs-diskstats @@ -0,0 +1,22 @@ +What: /proc/diskstats +Date: February 2008 +Contact: Jerome Marchand <jmarchan@redhat.com> +Description: + The /proc/diskstats file displays the I/O statistics + of block devices. Each line contains the following 14 + fields: + 1 - major number + 2 - minor mumber + 3 - device name + 4 - reads completed succesfully + 5 - reads merged + 6 - sectors read + 7 - time spent reading (ms) + 8 - writes completed + 9 - writes merged + 10 - sectors written + 11 - time spent writing (ms) + 12 - I/Os currently in progress + 13 - time spent doing I/Os (ms) + 14 - weighted time spent doing I/Os (ms) + For more details refer to Documentation/iostats.txt diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block new file mode 100644 index 000000000000..4bd9ea539129 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-block @@ -0,0 +1,28 @@ +What: /sys/block/<disk>/stat +Date: February 2008 +Contact: Jerome Marchand <jmarchan@redhat.com> +Description: + The /sys/block/<disk>/stat files displays the I/O + statistics of disk <disk>. They contain 11 fields: + 1 - reads completed succesfully + 2 - reads merged + 3 - sectors read + 4 - time spent reading (ms) + 5 - writes completed + 6 - writes merged + 7 - sectors written + 8 - time spent writing (ms) + 9 - I/Os currently in progress + 10 - time spent doing I/Os (ms) + 11 - weighted time spent doing I/Os (ms) + For more details refer Documentation/iostats.txt + + +What: /sys/block/<disk>/<part>/stat +Date: February 2008 +Contact: Jerome Marchand <jmarchan@redhat.com> +Description: + The /sys/block/<disk>/<part>/stat files display the + I/O statistics of partition <part>. The format is the + same as the above-written /sys/block/<disk>/stat + format. diff --git a/Documentation/iostats.txt b/Documentation/iostats.txt index b963c3b4afa5..5925c3cd030d 100644 --- a/Documentation/iostats.txt +++ b/Documentation/iostats.txt @@ -58,7 +58,7 @@ they should not wrap twice before you notice them. Each set of stats only applies to the indicated device; if you want system-wide stats you'll have to find all the devices and sum them all up. -Field 1 -- # of reads issued +Field 1 -- # of reads completed This is the total number of reads completed successfully. Field 2 -- # of reads merged, field 6 -- # of writes merged Reads and writes which are adjacent to each other may be merged for @@ -132,6 +132,19 @@ words, the number of reads for partitions is counted slightly before time of queuing for partitions, and at completion for whole disks. This is a subtle distinction that is probably uninteresting for most cases. +More significant is the error induced by counting the numbers of +reads/writes before merges for partitions and after for disks. Since a +typical workload usually contains a lot of successive and adjacent requests, +the number of reads/writes issued can be several times higher than the +number of reads/writes completed. + +In 2.6.25, the full statistic set is again available for partitions and +disk and partition statistics are consistent again. Since we still don't +keep record of the partition-relative address, an operation is attributed to +the partition which contains the first sector of the request after the +eventual merges. As requests can be merged across partition, this could lead +to some (probably insignificant) innacuracy. + Additional notes ---------------- |