What: /sys/class/bdi// Date: January 2008 Contact: Peter Zijlstra Description: Provide a place in sysfs for the backing_dev_info object. This allows setting and retrieving various BDI specific variables. The identifier can be either of the following: MAJOR:MINOR Device number for block devices, or value of st_dev on non-block filesystems which provide their own BDI, such as NFS and FUSE. MAJOR:MINOR-fuseblk Value of st_dev on fuseblk filesystems. default The default backing dev, used for non-block device backed filesystems which do not provide their own BDI. What: /sys/class/bdi//read_ahead_kb Date: January 2008 Contact: Peter Zijlstra Description: Size of the read-ahead window in kilobytes (read-write) What: /sys/class/bdi//min_ratio Date: January 2008 Contact: Peter Zijlstra Description: Under normal circumstances each device is given a part of the total write-back cache that relates to its current average writeout speed in relation to the other devices. The 'min_ratio' parameter allows assigning a minimum percentage of the write-back cache to a particular device. For example, this is useful for providing a minimum QoS. (read-write) What: /sys/class/bdi//min_ratio_fine Date: November 2022 Contact: Stefan Roesch Description: Under normal circumstances each device is given a part of the total write-back cache that relates to its current average writeout speed in relation to the other devices. The 'min_ratio_fine' parameter allows assigning a minimum reserve of the write-back cache to a particular device. The value is expressed as part of 1 million. For example, this is useful for providing a minimum QoS. (read-write) What: /sys/class/bdi//max_ratio Date: January 2008 Contact: Peter Zijlstra Description: Allows limiting a particular device to use not more than the given percentage of the write-back cache. This is useful in situations where we want to avoid one device taking all or most of the write-back cache. For example in case of an NFS mount that is prone to get stuck, or a FUSE mount which cannot be trusted to play fair. (read-write) What: /sys/class/bdi//max_ratio_fine Date: November 2022 Contact: Stefan Roesch Description: Allows limiting a particular device to use not more than the given value of the write-back cache. The value is given as part of 1 million. This is useful in situations where we want to avoid one device taking all or most of the write-back cache. For example in case of an NFS mount that is prone to get stuck, or a FUSE mount which cannot be trusted to play fair. (read-write) What: /sys/class/bdi//min_bytes Date: October 2022 Contact: Stefan Roesch Description: Under normal circumstances each device is given a part of the total write-back cache that relates to its current average writeout speed in relation to the other devices. The 'min_bytes' parameter allows assigning a minimum percentage of the write-back cache to a particular device expressed in bytes. For example, this is useful for providing a minimum QoS. (read-write) What: /sys/class/bdi//max_bytes Date: October 2022 Contact: Stefan Roesch Description: Allows limiting a particular device to use not more than the given 'max_bytes' of the write-back cache. This is useful in situations where we want to avoid one device taking all or most of the write-back cache. For example in case of an NFS mount that is prone to get stuck, a FUSE mount which cannot be trusted to play fair, or a nbd device. (read-write) What: /sys/class/bdi//strict_limit Date: October 2022 Contact: Stefan Roesch Description: Forces per-BDI checks for the share of given device in the write-back cache even before the global background dirty limit is reached. This is useful in situations where the global limit is much higher than affordable for given relatively slow (or untrusted) device. Turning strictlimit on has no visible effect if max_ratio is equal to 100%. (read-write) What: /sys/class/bdi//stable_pages_required Date: January 2008 Contact: Peter Zijlstra Description: If set, the backing device requires that all pages comprising a write request must not be changed until writeout is complete. (read-only)