1 What: /sys/class/bdi/<bdi>/ 1 What: /sys/class/bdi/<bdi>/
2 Date: January 2008 2 Date: January 2008
3 Contact: Peter Zijlstra <a.p.zijlstra@ch 3 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
4 Description: 4 Description:
5 5
6 Provide a place in sysfs for the backing_dev_i 6 Provide a place in sysfs for the backing_dev_info object. This allows
7 setting and retrieving various BDI specific va 7 setting and retrieving various BDI specific variables.
8 8
9 The <bdi> identifier can be either of the foll 9 The <bdi> identifier can be either of the following:
10 10
11 MAJOR:MINOR 11 MAJOR:MINOR
12 12
13 Device number for block devices, or va 13 Device number for block devices, or value of st_dev on
14 non-block filesystems which provide th 14 non-block filesystems which provide their own BDI, such as NFS
15 and FUSE. 15 and FUSE.
16 16
17 MAJOR:MINOR-fuseblk 17 MAJOR:MINOR-fuseblk
18 18
19 Value of st_dev on fuseblk filesystems 19 Value of st_dev on fuseblk filesystems.
20 20
21 default 21 default
22 22
23 The default backing dev, used for non- 23 The default backing dev, used for non-block device backed
24 filesystems which do not provide their 24 filesystems which do not provide their own BDI.
25 25
26 What: /sys/class/bdi/<bdi>/read_ahea !! 26 Files under /sys/class/bdi/<bdi>/
27 Date: January 2008 !! 27 ---------------------------------
28 Contact: Peter Zijlstra <a.p.zijlstra@ch !! 28
29 Description: !! 29 read_ahead_kb (read-write)
>> 30
30 Size of the read-ahead window in kilob 31 Size of the read-ahead window in kilobytes
31 32
32 (read-write) !! 33 min_ratio (read-write)
33 What: /sys/class/bdi/<bdi>/min_ratio !! 34
34 Date: January 2008 <<
35 Contact: Peter Zijlstra <a.p.zijlstra@ch <<
36 Description: <<
37 Under normal circumstances each device 35 Under normal circumstances each device is given a part of the
38 total write-back cache that relates to 36 total write-back cache that relates to its current average
39 writeout speed in relation to the othe 37 writeout speed in relation to the other devices.
40 38
41 The 'min_ratio' parameter allows assig 39 The 'min_ratio' parameter allows assigning a minimum
42 percentage of the write-back cache to 40 percentage of the write-back cache to a particular device.
43 For example, this is useful for provid 41 For example, this is useful for providing a minimum QoS.
44 42
45 (read-write) !! 43 max_ratio (read-write)
46 44
47 What: /sys/class/bdi/<bdi>/min_ratio <<
48 Date: November 2022 <<
49 Contact: Stefan Roesch <shr@devkernel.io <<
50 Description: <<
51 Under normal circumstances each device <<
52 total write-back cache that relates to <<
53 writeout speed in relation to the othe <<
54 <<
55 The 'min_ratio_fine' parameter allows <<
56 of the write-back cache to a particula <<
57 expressed as part of 1 million. For ex <<
58 providing a minimum QoS. <<
59 <<
60 (read-write) <<
61 <<
62 What: /sys/class/bdi/<bdi>/max_ratio <<
63 Date: January 2008 <<
64 Contact: Peter Zijlstra <a.p.zijlstra@ch <<
65 Description: <<
66 Allows limiting a particular device to 45 Allows limiting a particular device to use not more than the
67 given percentage of the write-back cac 46 given percentage of the write-back cache. This is useful in
68 situations where we want to avoid one 47 situations where we want to avoid one device taking all or
69 most of the write-back cache. For exa 48 most of the write-back cache. For example in case of an NFS
70 mount that is prone to get stuck, or a 49 mount that is prone to get stuck, or a FUSE mount which cannot
71 be trusted to play fair. 50 be trusted to play fair.
72 51
73 (read-write) !! 52 stable_pages_required (read-only)
74 53
75 What: /sys/class/bdi/<bdi>/max_ratio <<
76 Date: November 2022 <<
77 Contact: Stefan Roesch <shr@devkernel.io <<
78 Description: <<
79 Allows limiting a particular device to <<
80 given value of the write-back cache. <<
81 of 1 million. This is useful in situat <<
82 one device taking all or most of the w <<
83 in case of an NFS mount that is prone <<
84 which cannot be trusted to play fair. <<
85 <<
86 (read-write) <<
87 <<
88 What: /sys/class/bdi/<bdi>/min_bytes <<
89 Date: October 2022 <<
90 Contact: Stefan Roesch <shr@devkernel.io <<
91 Description: <<
92 Under normal circumstances each device <<
93 total write-back cache that relates to <<
94 writeout speed in relation to the othe <<
95 <<
96 The 'min_bytes' parameter allows assig <<
97 percentage of the write-back cache to <<
98 expressed in bytes. <<
99 For example, this is useful for provid <<
100 <<
101 (read-write) <<
102 <<
103 What: /sys/class/bdi/<bdi>/max_bytes <<
104 Date: October 2022 <<
105 Contact: Stefan Roesch <shr@devkernel.io <<
106 Description: <<
107 Allows limiting a particular device to <<
108 given 'max_bytes' of the write-back ca <<
109 situations where we want to avoid one <<
110 most of the write-back cache. For exa <<
111 mount that is prone to get stuck, a FU <<
112 trusted to play fair, or a nbd device. <<
113 <<
114 (read-write) <<
115 <<
116 What: /sys/class/bdi/<bdi>/strict_li <<
117 Date: October 2022 <<
118 Contact: Stefan Roesch <shr@devkernel.io <<
119 Description: <<
120 Forces per-BDI checks for the share of <<
121 cache even before the global backgroun <<
122 is useful in situations where the glob <<
123 affordable for given relatively slow ( <<
124 strictlimit on has no visible effect i <<
125 <<
126 (read-write) <<
127 What: /sys/class/bdi/<bdi>/stable_pa <<
128 Date: January 2008 <<
129 Contact: Peter Zijlstra <a.p.zijlstra@ch <<
130 Description: <<
131 If set, the backing device requires th 54 If set, the backing device requires that all pages comprising a write
132 request must not be changed until writ 55 request must not be changed until writeout is complete.
133 <<
134 (read-only) <<
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