1cf0ca9feSPeter ZijlstraWhat: /sys/class/bdi/<bdi>/ 2cf0ca9feSPeter ZijlstraDate: January 2008 3cf0ca9feSPeter ZijlstraContact: Peter Zijlstra <a.p.zijlstra@chello.nl> 4cf0ca9feSPeter ZijlstraDescription: 5cf0ca9feSPeter Zijlstra 676f1418bSMiklos SzerediProvide a place in sysfs for the backing_dev_info object. This allows 776f1418bSMiklos Szeredisetting and retrieving various BDI specific variables. 8cf0ca9feSPeter Zijlstra 9cf0ca9feSPeter ZijlstraThe <bdi> identifier can be either of the following: 10cf0ca9feSPeter Zijlstra 11cf0ca9feSPeter ZijlstraMAJOR:MINOR 12cf0ca9feSPeter Zijlstra 13cf0ca9feSPeter Zijlstra Device number for block devices, or value of st_dev on 14cf0ca9feSPeter Zijlstra non-block filesystems which provide their own BDI, such as NFS 15cf0ca9feSPeter Zijlstra and FUSE. 16cf0ca9feSPeter Zijlstra 1703fb0bceSMiklos SzerediMAJOR:MINOR-fuseblk 1803fb0bceSMiklos Szeredi 1903fb0bceSMiklos Szeredi Value of st_dev on fuseblk filesystems. 2003fb0bceSMiklos Szeredi 21cf0ca9feSPeter Zijlstradefault 22cf0ca9feSPeter Zijlstra 23cf0ca9feSPeter Zijlstra The default backing dev, used for non-block device backed 24cf0ca9feSPeter Zijlstra filesystems which do not provide their own BDI. 25cf0ca9feSPeter Zijlstra 26*8a609589SMauro Carvalho ChehabWhat: /sys/class/bdi/<bdi>/read_ahead_kb 27*8a609589SMauro Carvalho ChehabDate: January 2008 28*8a609589SMauro Carvalho ChehabContact: Peter Zijlstra <a.p.zijlstra@chello.nl> 29*8a609589SMauro Carvalho ChehabDescription: 30cf0ca9feSPeter Zijlstra Size of the read-ahead window in kilobytes 31cf0ca9feSPeter Zijlstra 32*8a609589SMauro Carvalho Chehab (read-write) 33*8a609589SMauro Carvalho ChehabWhat: /sys/class/bdi/<bdi>/min_ratio 34*8a609589SMauro Carvalho ChehabDate: January 2008 35*8a609589SMauro Carvalho ChehabContact: Peter Zijlstra <a.p.zijlstra@chello.nl> 36*8a609589SMauro Carvalho ChehabDescription: 3776f1418bSMiklos Szeredi Under normal circumstances each device is given a part of the 3876f1418bSMiklos Szeredi total write-back cache that relates to its current average 3976f1418bSMiklos Szeredi writeout speed in relation to the other devices. 4076f1418bSMiklos Szeredi 4176f1418bSMiklos Szeredi The 'min_ratio' parameter allows assigning a minimum 4276f1418bSMiklos Szeredi percentage of the write-back cache to a particular device. 4376f1418bSMiklos Szeredi For example, this is useful for providing a minimum QoS. 44a42dde04SPeter Zijlstra 45*8a609589SMauro Carvalho Chehab (read-write) 46a42dde04SPeter Zijlstra 47*8a609589SMauro Carvalho ChehabWhat: /sys/class/bdi/<bdi>/max_ratio 48*8a609589SMauro Carvalho ChehabDate: January 2008 49*8a609589SMauro Carvalho ChehabContact: Peter Zijlstra <a.p.zijlstra@chello.nl> 50*8a609589SMauro Carvalho ChehabDescription: 5176f1418bSMiklos Szeredi Allows limiting a particular device to use not more than the 5276f1418bSMiklos Szeredi given percentage of the write-back cache. This is useful in 5376f1418bSMiklos Szeredi situations where we want to avoid one device taking all or 5476f1418bSMiklos Szeredi most of the write-back cache. For example in case of an NFS 5576f1418bSMiklos Szeredi mount that is prone to get stuck, or a FUSE mount which cannot 5676f1418bSMiklos Szeredi be trusted to play fair. 577d311cdaSDarrick J. Wong 58*8a609589SMauro Carvalho Chehab (read-write) 59*8a609589SMauro Carvalho ChehabWhat: /sys/class/bdi/<bdi>/stable_pages_required 60*8a609589SMauro Carvalho ChehabDate: January 2008 61*8a609589SMauro Carvalho ChehabContact: Peter Zijlstra <a.p.zijlstra@chello.nl> 62*8a609589SMauro Carvalho ChehabDescription: 637d311cdaSDarrick J. Wong If set, the backing device requires that all pages comprising a write 647d311cdaSDarrick J. Wong request must not be changed until writeout is complete. 65*8a609589SMauro Carvalho Chehab 66*8a609589SMauro Carvalho Chehab (read-only) 67