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1What: /sys/class/bdi/<bdi>/
2Date: January 2008
3Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
4Description:
5
6Provide a place in sysfs for the backing_dev_info object. This allows
7setting and retrieving various BDI specific variables.
8
9The <bdi> identifier can be either of the following:
10
11MAJOR:MINOR
12
13 Device number for block devices, or value of st_dev on
14 non-block filesystems which provide their own BDI, such as NFS
15 and FUSE.
16
17MAJOR:MINOR-fuseblk
18
19 Value of st_dev on fuseblk filesystems.
20
21default
22
23 The default backing dev, used for non-block device backed
24 filesystems which do not provide their own BDI.
25
26What: /sys/class/bdi/<bdi>/read_ahead_kb
27Date: January 2008
28Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
29Description:
30 Size of the read-ahead window in kilobytes
31
32 (read-write)
33What: /sys/class/bdi/<bdi>/min_ratio
34Date: January 2008
35Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
36Description:
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.
40
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.
44
45 (read-write)
46
47What: /sys/class/bdi/<bdi>/max_ratio
48Date: January 2008
49Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
50Description:
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.
57
58 (read-write)
59What: /sys/class/bdi/<bdi>/stable_pages_required
60Date: January 2008
61Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
62Description:
63 If set, the backing device requires that all pages comprising a write
64 request must not be changed until writeout is complete.
65
66 (read-only)