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path: root/Documentation/block/cfq-iosched.txt
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2016-11-01block: replace REQ_NOIDLE with REQ_IDLEChristoph Hellwig
Noidle should be the default for writes as seen by all the compounds definitions in fs.h using it. In fact only direct I/O really should be using NODILE, so turn the whole flag around to get the defaults right, which will make our life much easier especially onces the WRITE_* defines go away. This assumes all the existing "raw" users of REQ_SYNC for writes want noidle behavior, which seems to be spot on from a quick audit. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-12-10Fix CFQ I/O scheduler parameter name in documentationLibor Pechacek
As seen in block/cfq-iosched.c, the parameter name is low_latency. Signed-off-by: Libor Pechacek <lpechacek@suse.cz> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2013-07-25doc: Fix typo in doucmentationsMasanari Iida
Correct typo (double words) in documentations. Signed-off-by: Masanari Iida <standby24x7@gmail.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2013-04-09Documentation: cfq-iosched: update documentation help for cfq tunablesNamjae Jeon
Add the documentation text for latency, target_latency & group_idle tunnable parameters in the block/cfq-iosched.txt. Also fix few typo(spelling) mistakes. Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com> Language somewhat modified by Jens. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2013-01-09cfq-iosched: enable full blkcg hierarchy supportTejun Heo
With the previous two patches, all cfqg scheduling decisions are based on vfraction and ready for hierarchy support. The only thing which keeps the behavior flat is cfqg_flat_parent() which makes vfraction calculation consider all non-root cfqgs children of the root cfqg. Replace it with cfqg_parent() which returns the real parent. This enables full blkcg hierarchy support for cfq-iosched. For example, consider the following hierarchy. root / \ A:500 B:250 / \ AA:500 AB:1000 For simplicity, let's say all the leaf nodes have active tasks and are on service tree. For each leaf node, vfraction would be AA: (500 / 1500) * (500 / 750) =~ 0.2222 AB: (1000 / 1500) * (500 / 750) =~ 0.4444 B: (250 / 750) =~ 0.3333 and vdisktime will be distributed accordingly. For more detail, please refer to Documentation/block/cfq-iosched.txt. v2: cfq-iosched.txt updated to describe group scheduling as suggested by Vivek. v3: blkio-controller.txt updated. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Vivek Goyal <vgoyal@redhat.com>
2012-08-09Documentation: update tunable options in block/cfq-iosched.txtNamjae Jeon
Update tunable options in block/cfq-iosched.txt. Signed-off-by: Namjae Jeon <linkinjeon@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2011-08-05cfq-iosched: Add documentation about idlingVivek Goyal
There are always questions about why CFQ is idling on various conditions. Recent ones is Christoph asking again why to idle on REQ_NOIDLE. His assertion is that XFS is relying more and more on workqueues and is concerned that CFQ idling on IO from every workqueue will impact XFS badly. So he suggested that I add some more documentation about CFQ idling and that can provide more clarity on the topic and also gives an opprotunity to poke a hole in theory and lead to improvements. So here is my attempt at that. Any comments are welcome. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-23cfq-iosched: Documentation help for new tunablesVivek Goyal
Some documentation to provide help with tunables. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>