From 76cb841cb886eef6b3bee341a2266c76578724ad Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 6 May 2024 03:02:30 +0200 Subject: Adding upstream version 4.19.249. Signed-off-by: Daniel Baumann --- Documentation/ABI/testing/sysfs-class-bdi | 55 +++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-bdi (limited to 'Documentation/ABI/testing/sysfs-class-bdi') diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi new file mode 100644 index 000000000..d773d5697 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-bdi @@ -0,0 +1,55 @@ +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. + +Files under /sys/class/bdi// +--------------------------------- + +read_ahead_kb (read-write) + + Size of the read-ahead window in kilobytes + +min_ratio (read-write) + + 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. + +max_ratio (read-write) + + 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. + +stable_pages_required (read-only) + + If set, the backing device requires that all pages comprising a write + request must not be changed until writeout is complete. -- cgit v1.2.3