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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.
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