• Markus Stockhausen's avatar
    md/raid5: activate raid6 rmw feature · 584acdd4
    Markus Stockhausen authored
    Glue it altogehter. The raid6 rmw path should work the same as the
    already existing raid5 logic. So emulate the prexor handling/flags
    and split functions as needed.
    1) Enable xor_syndrome() in the async layer.
    2) Split ops_run_prexor() into RAID4/5 and RAID6 logic. Xor the syndrome
    at the start of a rmw run as we did it before for the single parity.
    3) Take care of rmw run in ops_run_reconstruct6(). Again process only
    the changed pages to get syndrome back into sync.
    4) Enhance set_syndrome_sources() to fill NULL pages if we are in a rmw
    run. The lower layers will calculate start & end pages from that and
    call the xor_syndrome() correspondingly.
    5) Adapt the several places where we ignored Q handling up to now.
    Performance numbers for a single E5630 system with a mix of 10 7200k
    desktop/server disks. 300 seconds random write with 8 threads onto a
    3,2TB (10*400GB) RAID6 64K chunk without spare (group_thread_cnt=4)
    bsize   rmw_level=1   rmw_level=0   rmw_level=1   rmw_level=0
            skip_copy=1   skip_copy=1   skip_copy=0   skip_copy=0
       4K      115 KB/s      141 KB/s      165 KB/s      140 KB/s
       8K      225 KB/s      275 KB/s      324 KB/s      274 KB/s
      16K      434 KB/s      536 KB/s      640 KB/s      534 KB/s
      32K      751 KB/s    1,051 KB/s    1,234 KB/s    1,045 KB/s
      64K    1,339 KB/s    1,958 KB/s    2,282 KB/s    1,962 KB/s
     128K    2,673 KB/s    3,862 KB/s    4,113 KB/s    3,898 KB/s
     256K    7,685 KB/s    7,539 KB/s    7,557 KB/s    7,638 KB/s
     512K   19,556 KB/s   19,558 KB/s   19,652 KB/s   19,688 Kb/s
    Signed-off-by: default avatarMarkus Stockhausen <stockhausen@collogia.de>
    Signed-off-by: default avatarNeilBrown <neilb@suse.de>
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