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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>/min_ratio_fine
48Date: November 2022
49Contact: Stefan Roesch <shr@devkernel.io>
50Description:
51 Under normal circumstances each device is given a part of the
52 total write-back cache that relates to its current average
53 writeout speed in relation to the other devices.
54
55 The 'min_ratio_fine' parameter allows assigning a minimum reserve
56 of the write-back cache to a particular device. The value is
57 expressed as part of 1 million. For example, this is useful for
58 providing a minimum QoS.
59
60 (read-write)
61
62What: /sys/class/bdi/<bdi>/max_ratio
63Date: January 2008
64Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
65Description:
66 Allows limiting a particular device to use not more than the
67 given percentage of the write-back cache. This is useful in
68 situations where we want to avoid one device taking all or
69 most of the write-back cache. For example in case of an NFS
70 mount that is prone to get stuck, or a FUSE mount which cannot
71 be trusted to play fair.
72
73 (read-write)
74
75What: /sys/class/bdi/<bdi>/max_ratio_fine
76Date: November 2022
77Contact: Stefan Roesch <shr@devkernel.io>
78Description:
79 Allows limiting a particular device to use not more than the
80 given value of the write-back cache. The value is given as part
81 of 1 million. This is useful in situations where we want to avoid
82 one device taking all or most of the write-back cache. For example
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.
85
86 (read-write)
87
88What: /sys/class/bdi/<bdi>/min_bytes
89Date: October 2022
90Contact: Stefan Roesch <shr@devkernel.io>
91Description:
92 Under normal circumstances each device is given a part of the
93 total write-back cache that relates to its current average
94 writeout speed in relation to the other devices.
95
96 The 'min_bytes' parameter allows assigning a minimum
97 percentage of the write-back cache to a particular device
98 expressed in bytes.
99 For example, this is useful for providing a minimum QoS.
100
101 (read-write)
102
103What: /sys/class/bdi/<bdi>/max_bytes
104Date: October 2022
105Contact: Stefan Roesch <shr@devkernel.io>
106Description:
107 Allows limiting a particular device to use not more than the
108 given 'max_bytes' of the write-back cache. This is useful in
109 situations where we want to avoid one device taking all or
110 most of the write-back cache. For example in case of an NFS
111 mount that is prone to get stuck, a FUSE mount which cannot be
112 trusted to play fair, or a nbd device.
113
114 (read-write)
115
116What: /sys/class/bdi/<bdi>/strict_limit
117Date: October 2022
118Contact: Stefan Roesch <shr@devkernel.io>
119Description:
120 Forces per-BDI checks for the share of given device in the write-back
121 cache even before the global background dirty limit is reached. This
122 is useful in situations where the global limit is much higher than
123 affordable for given relatively slow (or untrusted) device. Turning
124 strictlimit on has no visible effect if max_ratio is equal to 100%.
125
126 (read-write)
127What: /sys/class/bdi/<bdi>/stable_pages_required
128Date: January 2008
129Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
130Description:
131 If set, the backing device requires that all pages comprising a write
132 request must not be changed until writeout is complete.
133
134 (read-only)
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
26Files under /sys/class/bdi/<bdi>/
27---------------------------------
28
29read_ahead_kb (read-write)
30
31 Size of the read-ahead window in kilobytes
32
33min_ratio (read-write)
34
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.
42
43max_ratio (read-write)
44
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.