Commit | Line | Data |
---|---|---|
cf0ca9fe PZ |
1 | What: /sys/class/bdi/<bdi>/ |
2 | Date: January 2008 | |
3 | Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> | |
4 | Description: | |
5 | ||
76f1418b MS |
6 | Provide a place in sysfs for the backing_dev_info object. This allows |
7 | setting and retrieving various BDI specific variables. | |
cf0ca9fe PZ |
8 | |
9 | The <bdi> identifier can be either of the following: | |
10 | ||
11 | MAJOR: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 | ||
03fb0bce MS |
17 | MAJOR:MINOR-fuseblk |
18 | ||
19 | Value of st_dev on fuseblk filesystems. | |
20 | ||
cf0ca9fe PZ |
21 | default |
22 | ||
23 | The default backing dev, used for non-block device backed | |
24 | filesystems which do not provide their own BDI. | |
25 | ||
26 | Files under /sys/class/bdi/<bdi>/ | |
27 | --------------------------------- | |
28 | ||
29 | read_ahead_kb (read-write) | |
30 | ||
31 | Size of the read-ahead window in kilobytes | |
32 | ||
189d3c4a PZ |
33 | min_ratio (read-write) |
34 | ||
76f1418b MS |
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. | |
38 | ||
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. | |
a42dde04 PZ |
42 | |
43 | max_ratio (read-write) | |
44 | ||
76f1418b MS |
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. | |
7d311cda DW |
51 | |
52 | stable_pages_required (read-only) | |
53 | ||
54 | If set, the backing device requires that all pages comprising a write | |
55 | request must not be changed until writeout is complete. |