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 Files under /sys/class/bdi/<bdi>/
27 ---------------------------------
29 read_ahead_kb (read-write)
31 Size of the read-ahead window in kilobytes
33 min_ratio (read-write)
35 Under normal circumstances each device is given a part of the
36 total write-back cache that relates to its current average
37 writeout speed in relation to the other devices.
39 The 'min_ratio' parameter allows assigning a minimum
40 percentage of the write-back cache to a particular device.
41 For example, this is useful for providing a minimum QoS.
43 max_ratio (read-write)
45 Allows limiting a particular device to use not more than the
46 given percentage of the write-back cache. This is useful in
47 situations where we want to avoid one device taking all or
48 most of the write-back cache. For example in case of an NFS
49 mount that is prone to get stuck, or a FUSE mount which cannot
50 be trusted to play fair.
52 stable_pages_required (read-only)
54 If set, the backing device requires that all pages comprising a write
55 request must not be changed until writeout is complete.