56 lines
1.6 KiB
Text
56 lines
1.6 KiB
Text
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What: /sys/class/bdi/<bdi>/
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Date: January 2008
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Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Description:
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Provide a place in sysfs for the backing_dev_info object. This allows
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setting and retrieving various BDI specific variables.
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The <bdi> identifier can be either of the following:
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MAJOR:MINOR
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Device number for block devices, or value of st_dev on
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non-block filesystems which provide their own BDI, such as NFS
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and FUSE.
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MAJOR:MINOR-fuseblk
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Value of st_dev on fuseblk filesystems.
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default
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The default backing dev, used for non-block device backed
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filesystems which do not provide their own BDI.
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Files under /sys/class/bdi/<bdi>/
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---------------------------------
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read_ahead_kb (read-write)
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Size of the read-ahead window in kilobytes
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min_ratio (read-write)
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Under normal circumstances each device is given a part of the
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total write-back cache that relates to its current average
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writeout speed in relation to the other devices.
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The 'min_ratio' parameter allows assigning a minimum
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percentage of the write-back cache to a particular device.
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For example, this is useful for providing a minimum QoS.
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max_ratio (read-write)
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Allows limiting a particular device to use not more than the
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given percentage of the write-back cache. This is useful in
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situations where we want to avoid one device taking all or
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most of the write-back cache. For example in case of an NFS
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mount that is prone to get stuck, or a FUSE mount which cannot
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be trusted to play fair.
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stable_pages_required (read-only)
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If set, the backing device requires that all pages comprising a write
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request must not be changed until writeout is complete.
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