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 What: /sys/class/bdi/<bdi>/read_ahead_kb
27 Date: January 2008 27 Date: January 2008
28 Contact: Peter Zijlstra <a.p.zijlstra@ch 28 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
29 Description: 29 Description:
30 Size of the read-ahead window in kilob 30 Size of the read-ahead window in kilobytes
31 31
32 (read-write) 32 (read-write)
33 What: /sys/class/bdi/<bdi>/min_ratio 33 What: /sys/class/bdi/<bdi>/min_ratio
34 Date: January 2008 34 Date: January 2008
35 Contact: Peter Zijlstra <a.p.zijlstra@ch 35 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
36 Description: 36 Description:
37 Under normal circumstances each device 37 Under normal circumstances each device is given a part of the
38 total write-back cache that relates to 38 total write-back cache that relates to its current average
39 writeout speed in relation to the othe 39 writeout speed in relation to the other devices.
40 40
41 The 'min_ratio' parameter allows assig 41 The 'min_ratio' parameter allows assigning a minimum
42 percentage of the write-back cache to 42 percentage of the write-back cache to a particular device.
43 For example, this is useful for provid 43 For example, this is useful for providing a minimum QoS.
44 44
45 (read-write) 45 (read-write)
46 46
47 What: /sys/class/bdi/<bdi>/min_ratio 47 What: /sys/class/bdi/<bdi>/min_ratio_fine
48 Date: November 2022 48 Date: November 2022
49 Contact: Stefan Roesch <shr@devkernel.io 49 Contact: Stefan Roesch <shr@devkernel.io>
50 Description: 50 Description:
51 Under normal circumstances each device 51 Under normal circumstances each device is given a part of the
52 total write-back cache that relates to 52 total write-back cache that relates to its current average
53 writeout speed in relation to the othe 53 writeout speed in relation to the other devices.
54 54
55 The 'min_ratio_fine' parameter allows 55 The 'min_ratio_fine' parameter allows assigning a minimum reserve
56 of the write-back cache to a particula 56 of the write-back cache to a particular device. The value is
57 expressed as part of 1 million. For ex 57 expressed as part of 1 million. For example, this is useful for
58 providing a minimum QoS. 58 providing a minimum QoS.
59 59
60 (read-write) 60 (read-write)
61 61
62 What: /sys/class/bdi/<bdi>/max_ratio 62 What: /sys/class/bdi/<bdi>/max_ratio
63 Date: January 2008 63 Date: January 2008
64 Contact: Peter Zijlstra <a.p.zijlstra@ch 64 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
65 Description: 65 Description:
66 Allows limiting a particular device to 66 Allows limiting a particular device to use not more than the
67 given percentage of the write-back cac 67 given percentage of the write-back cache. This is useful in
68 situations where we want to avoid one 68 situations where we want to avoid one device taking all or
69 most of the write-back cache. For exa 69 most of the write-back cache. For example in case of an NFS
70 mount that is prone to get stuck, or a 70 mount that is prone to get stuck, or a FUSE mount which cannot
71 be trusted to play fair. 71 be trusted to play fair.
72 72
73 (read-write) 73 (read-write)
74 74
75 What: /sys/class/bdi/<bdi>/max_ratio 75 What: /sys/class/bdi/<bdi>/max_ratio_fine
76 Date: November 2022 76 Date: November 2022
77 Contact: Stefan Roesch <shr@devkernel.io 77 Contact: Stefan Roesch <shr@devkernel.io>
78 Description: 78 Description:
79 Allows limiting a particular device to 79 Allows limiting a particular device to use not more than the
80 given value of the write-back cache. 80 given value of the write-back cache. The value is given as part
81 of 1 million. This is useful in situat 81 of 1 million. This is useful in situations where we want to avoid
82 one device taking all or most of the w 82 one device taking all or most of the write-back cache. For example
83 in case of an NFS mount that is prone 83 in case of an NFS mount that is prone to get stuck, or a FUSE mount
84 which cannot be trusted to play fair. 84 which cannot be trusted to play fair.
85 85
86 (read-write) 86 (read-write)
87 87
88 What: /sys/class/bdi/<bdi>/min_bytes 88 What: /sys/class/bdi/<bdi>/min_bytes
89 Date: October 2022 89 Date: October 2022
90 Contact: Stefan Roesch <shr@devkernel.io 90 Contact: Stefan Roesch <shr@devkernel.io>
91 Description: 91 Description:
92 Under normal circumstances each device 92 Under normal circumstances each device is given a part of the
93 total write-back cache that relates to 93 total write-back cache that relates to its current average
94 writeout speed in relation to the othe 94 writeout speed in relation to the other devices.
95 95
96 The 'min_bytes' parameter allows assig 96 The 'min_bytes' parameter allows assigning a minimum
97 percentage of the write-back cache to 97 percentage of the write-back cache to a particular device
98 expressed in bytes. 98 expressed in bytes.
99 For example, this is useful for provid 99 For example, this is useful for providing a minimum QoS.
100 100
101 (read-write) 101 (read-write)
102 102
103 What: /sys/class/bdi/<bdi>/max_bytes 103 What: /sys/class/bdi/<bdi>/max_bytes
104 Date: October 2022 104 Date: October 2022
105 Contact: Stefan Roesch <shr@devkernel.io 105 Contact: Stefan Roesch <shr@devkernel.io>
106 Description: 106 Description:
107 Allows limiting a particular device to 107 Allows limiting a particular device to use not more than the
108 given 'max_bytes' of the write-back ca 108 given 'max_bytes' of the write-back cache. This is useful in
109 situations where we want to avoid one 109 situations where we want to avoid one device taking all or
110 most of the write-back cache. For exa 110 most of the write-back cache. For example in case of an NFS
111 mount that is prone to get stuck, a FU 111 mount that is prone to get stuck, a FUSE mount which cannot be
112 trusted to play fair, or a nbd device. 112 trusted to play fair, or a nbd device.
113 113
114 (read-write) 114 (read-write)
115 115
116 What: /sys/class/bdi/<bdi>/strict_li 116 What: /sys/class/bdi/<bdi>/strict_limit
117 Date: October 2022 117 Date: October 2022
118 Contact: Stefan Roesch <shr@devkernel.io 118 Contact: Stefan Roesch <shr@devkernel.io>
119 Description: 119 Description:
120 Forces per-BDI checks for the share of 120 Forces per-BDI checks for the share of given device in the write-back
121 cache even before the global backgroun 121 cache even before the global background dirty limit is reached. This
122 is useful in situations where the glob 122 is useful in situations where the global limit is much higher than
123 affordable for given relatively slow ( 123 affordable for given relatively slow (or untrusted) device. Turning
124 strictlimit on has no visible effect i 124 strictlimit on has no visible effect if max_ratio is equal to 100%.
125 125
126 (read-write) 126 (read-write)
127 What: /sys/class/bdi/<bdi>/stable_pa 127 What: /sys/class/bdi/<bdi>/stable_pages_required
128 Date: January 2008 128 Date: January 2008
129 Contact: Peter Zijlstra <a.p.zijlstra@ch 129 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
130 Description: 130 Description:
131 If set, the backing device requires th 131 If set, the backing device requires that all pages comprising a write
132 request must not be changed until writ 132 request must not be changed until writeout is complete.
133 133
134 (read-only) 134 (read-only)
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