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2022-02-24Documentation: block/diskstats: update function namesNaohiro Aota1-3/+3
__make_request() and end_that_request_last() do no longer exist. Replace them with the current call-site. Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com> Reviwed-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220222012751.1933194-1-naohiro.aota@wdc.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-03-25block/diskstats: more accurate approximation of io_ticks for slow disksKonstantin Khlebnikov1-1/+4
Currently io_ticks is approximated by adding one at each start and end of requests if jiffies counter has changed. This works perfectly for requests shorter than a jiffy or if one of requests starts/ends at each jiffy. If disk executes just one request at a time and they are longer than two jiffies then only first and last jiffies will be accounted. Fix is simple: at the end of request add up into io_ticks jiffies passed since last update rather than just one jiffy. Example: common HDD executes random read 4k requests around 12ms. fio --name=test --filename=/dev/sdb --rw=randread --direct=1 --runtime=30 & iostat -x 10 sdb Note changes of iostat's "%util" 8,43% -> 99,99% before/after patch: Before: Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util sdb 0,00 0,00 82,60 0,00 330,40 0,00 8,00 0,96 12,09 12,09 0,00 1,02 8,43 After: Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util sdb 0,00 0,00 82,50 0,00 330,00 0,00 8,00 1,00 12,10 12,10 0,00 12,12 99,99 Now io_ticks does not loose time between start and end of requests, but for queue-depth > 1 some I/O time between adjacent starts might be lost. For load estimation "%util" is not as useful as average queue length, but it clearly shows how often disk queue is completely empty. Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to less precise counting") Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-12-02Merge tag 'docs-5.5a' of git://git.lwn.net/linuxLinus Torvalds1-23/+24
Pull Documentation updates from Jonathan Corbet: "Here are the main documentation changes for 5.5: - Various kerneldoc script enhancements. - More RST conversions; those are slowing down as we run out of things to convert, but we're a ways from done still. - Dan's "maintainer profile entry" work landed at last. Now we just need to get maintainers to fill in the profiles... - A reworking of the parallel build setup to work better with a variety of systems (and to not take over huge systems entirely in particular). - The MAINTAINERS file is now converted to RST during the build. Hopefully nobody ever tries to print this thing, or they will need to load a lot of paper. - A script and documentation making it easy for maintainers to add Link: tags at commit time. Also included is the removal of a bunch of spurious CR characters" * tag 'docs-5.5a' of git://git.lwn.net/linux: (91 commits) docs: remove a bunch of stray CRs docs: fix up the maintainer profile document libnvdimm, MAINTAINERS: Maintainer Entry Profile Maintainer Handbook: Maintainer Entry Profile MAINTAINERS: Reclaim the P: tag for Maintainer Entry Profile docs, parallelism: Rearrange how jobserver reservations are made docs, parallelism: Do not leak blocking mode to other readers docs, parallelism: Fix failure path and add comment Documentation: Remove bootmem_debug from kernel-parameters.txt Documentation: security: core.rst: fix warnings Documentation/process/howto/kokr: Update for 4.x -> 5.x versioning Documentation/translation: Use Korean for Korean translation title docs/memory-barriers.txt: Remove remaining references to mmiowb() docs/memory-barriers.txt/kokr: Update I/O section to be clearer about CPU vs thread docs/memory-barriers.txt/kokr: Fix style, spacing and grammar in I/O section Documentation/kokr: Kill all references to mmiowb() docs/memory-barriers.txt/kokr: Rewrite "KERNEL I/O BARRIER EFFECTS" section docs: Add initial documentation for devfreq Documentation: Document how to get links with git am docs: Add request_irq() documentation ...
2019-11-21block: add iostat counters for flush requestsKonstantin Khlebnikov1-0/+9
Requests that triggers flushing volatile writeback cache to disk (barriers) have significant effect to overall performance. Block layer has sophisticated engine for combining several flush requests into one. But there is no statistics for actual flushes executed by disk. Requests which trigger flushes usually are barriers - zero-size writes. This patch adds two iostat counters into /sys/class/block/$dev/stat and /proc/diskstats - count of completed flush requests and their total time. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-10-18Updated iostats docsAlbert Vaca Cintora1-23/+24
Previous docs mentioned 11 unsigned long fields, when the reality is that we have 15 fields with a mix of unsigned long and unsigned int. Signed-off-by: Albert Vaca Cintora <albertvaka@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-07-15docs: admin-guide: add a series of orphaned documentsMauro Carvalho Chehab1-0/+197
There are lots of documents that belong to the admin-guide but are on random places (most under Documentation root dir). Move them to the admin guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>