189d3c4a94
Under normal circumstances each device is given a part of the total write-back cache that relates to its current avg writeout speed in relation to the other devices. min_ratio - allows one to assign a minimum portion of the write-back cache to a particular device. This is useful in situations where you might want to provide a minimum QoS. (One request for this feature came from flash based storage people who wanted to avoid writing out at all costs - they of course needed some pdflush hacks as well) max_ratio - allows one to assign a maximum portion of the dirty limit to a particular device. This is useful in situations where you want to avoid one device taking all or most of the write-back cache. Eg. an NFS mount that is prone to get stuck, or a FUSE mount which you don't trust to play fair. Add "min_ratio" to /sys/class/bdi. This indicates the minimum percentage of the global dirty threshold allocated to this bdi. [mszeredi@suse.cz] - fix parsing in min_ratio_store() - document new sysfs attribute Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
53 lines
1.3 KiB
Plaintext
53 lines
1.3 KiB
Plaintext
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.
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This allows us to see and set the 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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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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reclaimable_kb (read-only)
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Reclaimable (dirty or unstable) memory destined for writeback
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to this device
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writeback_kb (read-only)
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Memory currently under writeback to this device
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dirty_kb (read-only)
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Global threshold for reclaimable + writeback memory
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bdi_dirty_kb (read-only)
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Current threshold on this BDI for reclaimable + writeback
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memory
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min_ratio (read-write)
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Minimal percentage of global dirty threshold allocated to this
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bdi. If the value written to this file would make the the sum
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of all min_ratio values exceed 100, then EINVAL is returned.
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The default is zero
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