block: improve ioprio class description comment

In include/usapi/linux/ioprio.h, change the ioprio class enum comment to remove the outdated reference to CFQ and mention BFQ and mq-deadline instead.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.

Damien Le Moal committed 5 years ago

Commit 25bca501 parent a680dd71 file · +6 −4Browse files

Unified · Split

include/uapi/linux/ioprio.h+6−4

@@ -13,10 +13,12 @@ · 12 unmodified lines
13	13	#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) \| data)
14	14
15	15	/*
16		− * These are the io priority groups as implemented by CFQ. RT is the realtime
17		− * class, it always gets premium service. BE is the best-effort scheduling
18		− * class, the default for any process. IDLE is the idle scheduling class, it
19		− * is only served when no one else is using the disk.
	16	+ * These are the io priority groups as implemented by the BFQ and mq-deadline
	17	+ * schedulers. RT is the realtime class, it always gets premium service. For
	18	+ * ATA disks supporting NCQ IO priority, RT class IOs will be processed using
	19	+ * high priority NCQ commands. BE is the best-effort scheduling class, the
	20	+ * default for any process. IDLE is the idle scheduling class, it is only
	21	+ * served when no one else is using the disk.
20	22	*/
21	23	enum {
22	24	IOPRIO_CLASS_NONE,