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| author | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-08 09:42:46 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-08 09:42:46 -0800 |
| commit | 03054de1e0b90b33e9974107d84dabd2509f5898 (patch) | |
| tree | a85e92d5387d94ef9e3d10bf11467136c681ad04 /Documentation/iostats.txt | |
| parent | b5eb9513f7c1bee862ada22bf1489f53752686bd (diff) | |
| parent | 0e53c2be0495afa97c6b0d06397adcbff9c65347 (diff) | |
| download | linux-03054de1e0b90b33e9974107d84dabd2509f5898.tar.gz | |
Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block
* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
Enhanced partition statistics: documentation update
Enhanced partition statistics: remove old partition statistics
Enhanced partition statistics: procfs
Enhanced partition statistics: sysfs
Enhanced partition statistics: aoe fix
Enhanced partition statistics: update partition statitics
Enhanced partition statistics: core statistics
block: fixup rq_init() a bit
Manually fixed conflict in drivers/block/aoe/aoecmd.c due to statistics
support.
Diffstat (limited to 'Documentation/iostats.txt')
| -rw-r--r-- | Documentation/iostats.txt | 15 |
1 files changed, 14 insertions, 1 deletions
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 ---------------- |