1 What: /sys/class/bdi/<bdi>/
3 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
6 Provide a place in sysfs for the backing_dev_info object. This allows
7 setting and retrieving various BDI specific variables.
9 The <bdi> identifier can be either of the following:
13 Device number for block devices, or value of st_dev on
14 non-block filesystems which provide their own BDI, such as NFS
19 Value of st_dev on fuseblk filesystems.
23 The default backing dev, used for non-block device backed
24 filesystems which do not provide their own BDI.
26 What: /sys/class/bdi/<bdi>/read_ahead_kb
28 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
30 Size of the read-ahead window in kilobytes
33 What: /sys/class/bdi/<bdi>/min_ratio
35 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
37 Under normal circumstances each device is given a part of the
38 total write-back cache that relates to its current average
39 writeout speed in relation to the other devices.
41 The 'min_ratio' parameter allows assigning a minimum
42 percentage of the write-back cache to a particular device.
43 For example, this is useful for providing a minimum QoS.
47 What: /sys/class/bdi/<bdi>/max_ratio
49 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
51 Allows limiting a particular device to use not more than the
52 given percentage of the write-back cache. This is useful in
53 situations where we want to avoid one device taking all or
54 most of the write-back cache. For example in case of an NFS
55 mount that is prone to get stuck, or a FUSE mount which cannot
56 be trusted to play fair.
59 What: /sys/class/bdi/<bdi>/stable_pages_required
61 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
63 If set, the backing device requires that all pages comprising a write
64 request must not be changed until writeout is complete.