docs: block: null_blk: enhance document style (04c56957) · Commits · 戴 / test

Documentation/block/null_blk.rst

+18 −15

Original line number	Original line	Diff line number	Diff line
			.. SPDX-License-Identifier: GPL-2.0

	========================		========================
	Null block device driver		Null block device driver
	========================		========================

	1. Overview		Overview
	===========		========

	The null block device (/dev/nullb*) is used for benchmarking the various		The null block device (``/dev/nullb*``) is used for benchmarking the various
	block-layer implementations. It emulates a block device of X gigabytes in size.		block-layer implementations. It emulates a block device of X gigabytes in size.
	The following instances are possible:		It does not execute any read/write operation, just mark them as complete in
			the request queue. The following instances are possible:
	Single-queue block-layer

	- Request-based.
	- Single submission queue per device.
	- Implements IO scheduling algorithms (CFQ, Deadline, noop).

	Multi-queue block-layer		Multi-queue block-layer

	@@ -27,15 +24,15 @@ The following instances are possible:

	All of them have a completion queue for each core in the system.		All of them have a completion queue for each core in the system.

	2. Module parameters applicable for all instances		Module parameters
	=================================================		=================

	queue_mode=[0-2]: Default: 2-Multi-queue		queue_mode=[0-2]: Default: 2-Multi-queue
	Selects which block-layer the module should instantiate with.		Selects which block-layer the module should instantiate with.

	= ============		= ============
	0 Bio-based		0 Bio-based
	1 Single-queue		1 Single-queue (deprecated)
	2 Multi-queue		2 Multi-queue
	= ============		= ============

	@@ -67,7 +64,7 @@ irqmode=[0-2]: Default: 1-Soft-irq
	completion_nsec=[ns]: Default: 10,000ns		completion_nsec=[ns]: Default: 10,000ns
	Combined with irqmode=2 (timer). The time each completion event must wait.		Combined with irqmode=2 (timer). The time each completion event must wait.

	submit_queues=[1..nr_cpus]:		submit_queues=[1..nr_cpus]: Default: 1
	The number of submission queues attached to the device driver. If unset, it		The number of submission queues attached to the device driver. If unset, it
	defaults to 1. For multi-queue, it is ignored when use_per_node_hctx module		defaults to 1. For multi-queue, it is ignored when use_per_node_hctx module
	parameter is 1.		parameter is 1.
	@@ -75,9 +72,11 @@ submit_queues=[1..nr_cpus]:
	hw_queue_depth=[0..qdepth]: Default: 64		hw_queue_depth=[0..qdepth]: Default: 64
	The hardware queue depth of the device.		The hardware queue depth of the device.

	III: Multi-queue specific parameters		Multi-queue specific parameters
			-------------------------------

	use_per_node_hctx=[0/1]: Default: 0		use_per_node_hctx=[0/1]: Default: 0
			Number of hardware context queues.

	= =====================================================================		= =====================================================================
	0 The number of submit queues are set to the value of the submit_queues		0 The number of submit queues are set to the value of the submit_queues
	@@ -87,6 +86,7 @@ use_per_node_hctx=[0/1]: Default: 0
	= =====================================================================		= =====================================================================

	no_sched=[0/1]: Default: 0		no_sched=[0/1]: Default: 0
			Enable/disable the io scheduler.

	= ======================================		= ======================================
	0 nullb* use default blk-mq io scheduler		0 nullb* use default blk-mq io scheduler
	@@ -94,6 +94,7 @@ no_sched=[0/1]: Default: 0
	= ======================================		= ======================================

	blocking=[0/1]: Default: 0		blocking=[0/1]: Default: 0
			Blocking behavior of the request queue.

	= ===============================================================		= ===============================================================
	0 Register as a non-blocking blk-mq driver device.		0 Register as a non-blocking blk-mq driver device.
	@@ -103,6 +104,7 @@ blocking=[0/1]: Default: 0
	= ===============================================================		= ===============================================================

	shared_tags=[0/1]: Default: 0		shared_tags=[0/1]: Default: 0
			Sharing tags between devices.

	= ================================================================		= ================================================================
	0 Tag set is not shared.		0 Tag set is not shared.
	@@ -111,6 +113,7 @@ shared_tags=[0/1]: Default: 0
	= ================================================================		= ================================================================

	zoned=[0/1]: Default: 0		zoned=[0/1]: Default: 0
			Device is a random-access or a zoned block device.

	= ======================================================================		= ======================================================================
	0 Block device is exposed as a random-access block device.		0 Block device is exposed as a random-access block device.

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