• Tony Battersby's avatar
    [SCSI] 3w-9xxx: fix abysmal write performance on some motherboards · 1e6c38ce
    Tony Battersby authored
    The 3ware 9500S-8 SATA RAID controller exhibits terrible write
    performance when PCI memory-write-and-invalidate is disabled.  This is
    easy to demonstrate by replacing pci_try_set_mwi() in the patch below
    with pci_clear_mwi().  My benchmarks show the following:
    
    MWI disabled: 15 MB/s write, 330 MB/s read
    MWI enabled:  240 MB/s write, 330 MB/s read
    
    Most motherboards will enable MWI without the driver having to set it
    explicitly, so most people probably wouldn't encounter this problem.
    For the few motherboards that don't enable it, this patch could give a
    16x performance improvement for writing.
    
    This issue does not seem to affect the 9550SX controller, but the patch
    doesn't hurt it either.  I haven't tested any of the other 3ware
    controllers.
    Signed-off-by: default avatarTony Battersby <tonyb@cybernetics.com>
    Acked-by: default avataradam radford <aradford@gmail.com>
    Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
    1e6c38ce
3w-9xxx.c 72.3 KB