• Peter Zijlstra's avatar
    mm: bdi: allow setting a minimum for the bdi dirty limit · 189d3c4a
    Peter Zijlstra authored
    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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    189d3c4a
sysfs-class-bdi 1.25 KB