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1What: /sys/class/bdi/<bdi>/2Date: January 20083Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>4Description:5 6Provide a place in sysfs for the backing_dev_info object. This allows7setting and retrieving various BDI specific variables.8 9The <bdi> identifier can be either of the following:10 11MAJOR:MINOR12 13 Device number for block devices, or value of st_dev on14 non-block filesystems which provide their own BDI, such as NFS15 and FUSE.16 17MAJOR:MINOR-fuseblk18 19 Value of st_dev on fuseblk filesystems.20 21default22 23 The default backing dev, used for non-block device backed24 filesystems which do not provide their own BDI.25 26What: /sys/class/bdi/<bdi>/read_ahead_kb27Date: January 200828Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>29Description:30 Size of the read-ahead window in kilobytes31 32 (read-write)33What: /sys/class/bdi/<bdi>/min_ratio34Date: January 200835Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>36Description:37 Under normal circumstances each device is given a part of the38 total write-back cache that relates to its current average39 writeout speed in relation to the other devices.40 41 The 'min_ratio' parameter allows assigning a minimum42 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_fine48Date: November 202249Contact: Stefan Roesch <shr@devkernel.io>50Description:51 Under normal circumstances each device is given a part of the52 total write-back cache that relates to its current average53 writeout speed in relation to the other devices.54 55 The 'min_ratio_fine' parameter allows assigning a minimum reserve56 of the write-back cache to a particular device. The value is57 expressed as part of 1 million. For example, this is useful for58 providing a minimum QoS.59 60 (read-write)61 62What: /sys/class/bdi/<bdi>/max_ratio63Date: January 200864Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>65Description:66 Allows limiting a particular device to use not more than the67 given percentage of the write-back cache. This is useful in68 situations where we want to avoid one device taking all or69 most of the write-back cache. For example in case of an NFS70 mount that is prone to get stuck, or a FUSE mount which cannot71 be trusted to play fair.72 73 (read-write)74 75What: /sys/class/bdi/<bdi>/max_ratio_fine76Date: November 202277Contact: Stefan Roesch <shr@devkernel.io>78Description:79 Allows limiting a particular device to use not more than the80 given value of the write-back cache. The value is given as part81 of 1 million. This is useful in situations where we want to avoid82 one device taking all or most of the write-back cache. For example83 in case of an NFS mount that is prone to get stuck, or a FUSE mount84 which cannot be trusted to play fair.85 86 (read-write)87 88What: /sys/class/bdi/<bdi>/min_bytes89Date: October 202290Contact: Stefan Roesch <shr@devkernel.io>91Description:92 Under normal circumstances each device is given a part of the93 total write-back cache that relates to its current average94 writeout speed in relation to the other devices.95 96 The 'min_bytes' parameter allows assigning a minimum97 percentage of the write-back cache to a particular device98 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_bytes104Date: October 2022105Contact: Stefan Roesch <shr@devkernel.io>106Description:107 Allows limiting a particular device to use not more than the108 given 'max_bytes' of the write-back cache. This is useful in109 situations where we want to avoid one device taking all or110 most of the write-back cache. For example in case of an NFS111 mount that is prone to get stuck, a FUSE mount which cannot be112 trusted to play fair, or a nbd device.113 114 (read-write)115 116What: /sys/class/bdi/<bdi>/strict_limit117Date: October 2022118Contact: Stefan Roesch <shr@devkernel.io>119Description:120 Forces per-BDI checks for the share of given device in the write-back121 cache even before the global background dirty limit is reached. This122 is useful in situations where the global limit is much higher than123 affordable for given relatively slow (or untrusted) device. Turning124 strictlimit on has no visible effect if max_ratio is equal to 100%.125 126 (read-write)127What: /sys/class/bdi/<bdi>/stable_pages_required128Date: January 2008129Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>130Description:131 If set, the backing device requires that all pages comprising a write132 request must not be changed until writeout is complete.133 134 (read-only)135