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Diffstat (limited to 'Documentation/ABI/testing/sysfs-class-bdi')
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1 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi new file mode 100644 index 000000000..6d2a2fc18 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-bdi @@ -0,0 +1,66 @@ +What: /sys/class/bdi/<bdi>/ +Date: January 2008 +Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> +Description: + +Provide a place in sysfs for the backing_dev_info object. This allows +setting and retrieving various BDI specific variables. + +The <bdi> 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/<bdi>/read_ahead_kb +Date: January 2008 +Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> +Description: + Size of the read-ahead window in kilobytes + + (read-write) +What: /sys/class/bdi/<bdi>/min_ratio +Date: January 2008 +Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> +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/<bdi>/max_ratio +Date: January 2008 +Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> +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/<bdi>/stable_pages_required +Date: January 2008 +Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> +Description: + If set, the backing device requires that all pages comprising a write + request must not be changed until writeout is complete. + + (read-only) |