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54 lines
1.6 KiB
54 lines
1.6 KiB
What: /sys/class/bdi/<bdi>/ |
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Date: January 2008 |
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Contact: Peter Zijlstra <[email protected]> |
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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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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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