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block: improve ioprio class description comment

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In include/usapi/linux/ioprio.h, change the ioprio class enum comment
to remove the outdated reference to CFQ and mention BFQ and mq-deadline
instead. Also document the high priority NCQ command use for RT class
IOs directed at ATA drives that support NCQ priority.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210811033702.368488-3-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Damien Le Moal 2021-08-11 12:36:58 +09:00 committed by Jens Axboe
parent a680dd72ec
commit 25bca50e52
1 changed files with 6 additions and 4 deletions
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10
include/uapi/linux/ioprio.h
View file

@ -13,10 +13,12 @@
#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
/*
* These are the io priority groups as implemented by CFQ. RT is the realtime
* class, it always gets premium service. BE is the best-effort scheduling
* class, the default for any process. IDLE is the idle scheduling class, it
* is only served when no one else is using the disk.
* These are the io priority groups as implemented by the BFQ and mq-deadline
* schedulers. RT is the realtime class, it always gets premium service. For
* ATA disks supporting NCQ IO priority, RT class IOs will be processed using
* high priority NCQ commands. BE is the best-effort scheduling class, the
* default for any process. IDLE is the idle scheduling class, it is only
* served when no one else is using the disk.
*/
enum {
IOPRIO_CLASS_NONE,