• NeilBrown's avatar
    md: add proper write-congestion reporting to RAID1 and RAID10. · 34db0cd6
    NeilBrown authored
    RAID1 and RAID10 handle write requests by queuing them for handling by
    a separate thread.  This is because when a write-intent-bitmap is
    active we might need to update the bitmap first, so it is good to
    queue a lot of writes, then do one big bitmap update for them all.
    However writeback request devices to appear to be congested after a
    while so it can make some guesstimate of throughput.  The infinite
    queue defeats that (note that RAID5 has already has a finite queue so
    it doesn't suffer from this problem).
    So impose a limit on the number of pending write requests.  By default
    it is 1024 which seems to be generally suitable.  Make it configurable
    via module option just in case someone finds a regression.
    Signed-off-by: default avatarNeilBrown <neilb@suse.de>
raid10.h 3.66 KB