Documentation/ABI/testing/sysfs-class-bdi

Source file repositories/reference/linux-study-clean/Documentation/ABI/testing/sysfs-class-bdi

File Facts

System
Linux kernel
Corpus path
Documentation/ABI/testing/sysfs-class-bdi
Extension
[no extension]
Size
4519 bytes
Lines
135
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: Documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

What:		/sys/class/bdi/<bdi>/
Date:		January 2008
Contact:	Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:

Provide a place in sysfs for the backing_dev_info object.  This allows
setting and retrieving various BDI specific variables.

The <bdi> identifier can be either of the following:

MAJOR:MINOR

	Device number for block devices, or value of st_dev on
	non-block filesystems which provide their own BDI, such as NFS
	and FUSE.

MAJOR:MINOR-fuseblk

	Value of st_dev on fuseblk filesystems.

default

	The default backing dev, used for non-block device backed
	filesystems which do not provide their own BDI.

What:		/sys/class/bdi/<bdi>/read_ahead_kb
Date:		January 2008
Contact:	Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
	Size of the read-ahead window in kilobytes

	(read-write)
What:		/sys/class/bdi/<bdi>/min_ratio
Date:		January 2008
Contact:	Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
	Under normal circumstances each device is given a part of the
	total write-back cache that relates to its current average
	writeout speed in relation to the other devices.

	The 'min_ratio' parameter allows assigning a minimum
	percentage of the write-back cache to a particular device.
	For example, this is useful for providing a minimum QoS.

	(read-write)

What:		/sys/class/bdi/<bdi>/min_ratio_fine
Date:		November 2022
Contact:	Stefan Roesch <shr@devkernel.io>
Description:
	Under normal circumstances each device is given a part of the
	total write-back cache that relates to its current average
	writeout speed in relation to the other devices.

	The 'min_ratio_fine' parameter allows assigning a minimum reserve
	of the write-back cache to a particular device. The value is
	expressed as part of 1 million. For example, this is useful for
	providing a minimum QoS.

	(read-write)

What:		/sys/class/bdi/<bdi>/max_ratio
Date:		January 2008
Contact:	Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
	Allows limiting a particular device to use not more than the
	given percentage of the write-back cache.  This is useful in
	situations where we want to avoid one device taking all or
	most of the write-back cache.  For example in case of an NFS
	mount that is prone to get stuck, or a FUSE mount which cannot

Annotation

Implementation Notes