1What: /sys/class/bdi/<bdi>/ 2Date: January 2008 3Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 4Description: 5 6Provide a place in sysfs for the backing_dev_info object. This allows 7setting and retrieving various BDI specific variables. 8 9The <bdi> identifier can be either of the following: 10 11MAJOR:MINOR 12 13 Device number for block devices, or value of st_dev on 14 non-block filesystems which provide their own BDI, such as NFS 15 and FUSE. 16 17MAJOR:MINOR-fuseblk 18 19 Value of st_dev on fuseblk filesystems. 20 21default 22 23 The default backing dev, used for non-block device backed 24 filesystems which do not provide their own BDI. 25 26What: /sys/class/bdi/<bdi>/read_ahead_kb 27Date: January 2008 28Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 29Description: 30 Size of the read-ahead window in kilobytes 31 32 (read-write) 33What: /sys/class/bdi/<bdi>/min_ratio 34Date: January 2008 35Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 36Description: 37 Under normal circumstances each device is given a part of the 38 total write-back cache that relates to its current average 39 writeout speed in relation to the other devices. 40 41 The 'min_ratio' parameter allows assigning a minimum 42 percentage of the write-back cache to a particular device. 43 For example, this is useful for providing a minimum QoS. 44 45 (read-write) 46 47What: /sys/class/bdi/<bdi>/max_ratio 48Date: January 2008 49Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 50Description: 51 Allows limiting a particular device to use not more than the 52 given percentage of the write-back cache. This is useful in 53 situations where we want to avoid one device taking all or 54 most of the write-back cache. For example in case of an NFS 55 mount that is prone to get stuck, or a FUSE mount which cannot 56 be trusted to play fair. 57 58 (read-write) 59What: /sys/class/bdi/<bdi>/stable_pages_required 60Date: January 2008 61Contact: Peter Zijlstra <a.p.zijlstra@chello.nl> 62Description: 63 If set, the backing device requires that all pages comprising a write 64 request must not be changed until writeout is complete. 65 66 (read-only) 67