1 What: /sys/class/bdi/<bdi>/ 2 Date: January 2008 3 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 4 Description: 5 6 Provide a place in sysfs for the backing_dev_info object. This allows 7 setting and retrieving various BDI specific variables. 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 17 MAJOR:MINOR-fuseblk 18 19 Value of st_dev on fuseblk filesystems. 20 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 What: /sys/class/bdi/<bdi>/read_ahead_kb 27 Date: January 2008 28 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 29 Description: 30 Size of the read-ahead window in kilobytes 31 32 (read-write) 33 What: /sys/class/bdi/<bdi>/min_ratio 34 Date: January 2008 35 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 36 Description: 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 47 What: /sys/class/bdi/<bdi>/min_ratio_fine 48 Date: November 2022 49 Contact: Stefan Roesch <shr@devkernel.io> 50 Description: 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 62 What: /sys/class/bdi/<bdi>/max_ratio 63 Date: January 2008 64 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 65 Description: 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 75 What: /sys/class/bdi/<bdi>/max_ratio_fine 76 Date: November 2022 77 Contact: Stefan Roesch <shr@devkernel.io> 78 Description: 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 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 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) 102 103 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 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) 115 116 What: /sys/class/bdi/<bdi>/strict_limit 117 Date: October 2022 118 Contact: Stefan Roesch <shr@devkernel.io> 119 Description: 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) 127 What: /sys/class/bdi/<bdi>/stable_pages_required 128 Date: January 2008 129 Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 130 Description: 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) 135