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.
|
|
Files under /sys/class/bdi/<bdi>/
|
|
read_ahead_kb (read-write)
|
|
Size of the read-ahead window in kilobytes
|
|
min_ratio (read-write)
|
|
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.
|
|
max_ratio (read-write)
|
|
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
|
be trusted to play fair.
|
|
stable_pages_required (read-only)
|
|
If set, the backing device requires that all pages comprising a write
|
request must not be changed until writeout is complete.
|
