ahd(4) poor performance

[Justin T. Gibbs]

Enable the write cache on your scsi disk or disable it on
your ata disk.

--
Justin

--On Saturday, June 24, 2006 12:25 AM +0300 Volodymyr Kostyrko 
<arcade at synergetica.dn.ua> wrote:

> Justin T. Gibbs wrote:
>> Access the raw device to bypass the filesystem and VM subsystem.
>> Start N dds where N is the queue depth you've configured for
>> the device.
>
>    I've made almost the same test on /dev/da0s1b (the swap partition).
>
>    Script:
>
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> dd if=/dev/zero of=/dev/da0s1b count=20480&
> wait
>
>  > camcontrol tags 0:0 -v
> (pass0:ahd0:0:0:0): dev_openings  8
> (pass0:ahd0:0:0:0): dev_active    8
> (pass0:ahd0:0:0:0): devq_openings 8
> (pass0:ahd0:0:0:0): devq_queued   0
> (pass0:ahd0:0:0:0): held          0
> (pass0:ahd0:0:0:0): mintags       2
> (pass0:ahd0:0:0:0): maxtags       255
>
>
>      2 users    Load  0.31  0.49  0.49                  23 ??? 21:13
>
> Mem:KB    REAL            VIRTUAL                     VN PAGER  SWAP PAGER
>          Tot   Share      Tot    Share    Free         in  out     in  out
> Act  106680   13672   316112    27816 1624096 count
> All  424236   19976 73870680    41352         pages
>
> Interrupts
> Proc:r  p  d  s  w    Csw  Trp  Sys  Int  Sof  Flt        cow    8190
> total
>             9 80      1541    9  553  555    2      144940 wire 4: sio0
>                                                      83608 act 14: ata
>   0.0%Sys   0.0%Intr  0.0%User  0.0%Nice 99.9%Idl   197908 inact     3
> 16: uhc
>|    |    |    |    |    |    |    |    |    |         12 cache 19: uhc
>                                                    1624084 free 20: em1
>                                                            daefr 23: ehc
> Namei         Name-cache    Dir-cache                     prcfr     3 32:
> em0
>      Calls     hits    %     hits    %                     react   196
> 66: ahd
>          4        4  100                                   pdwak 67: ahd
>                                            zfod            pdpgs  1997
> cpu0: time
> Disks   da0   da1 pass0 pass1             ozfod           intrn  1997
> cpu2: time
> KB/t   0.50  0.00  0.00  0.00             %slo-z   114464 buf    1997
> cpu1: time
> tps     195     0     0     0             tfree        51 dirty  1997
> cpu3: time
> MB/s   0.10  0.00  0.00  0.00                      100000 desiredvnodes
> % busy  100     0     0     0                        7750 numvnodes
>                                                       6193 freevnodes
>    Script output is:
>
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 363.641053 secs (28835 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 483.640098 secs (21681 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 483.650721 secs (21680 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 604.895852 secs (17335 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 618.500802 secs (16954 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 618.539979 secs (16952 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 618.545158 secs (16952 bytes/sec)
> 20480+0 records in
> 20480+0 records out
> 10485760 bytes transferred in 618.553915 secs (16952 bytes/sec)
>
>    Hmm... My ATA drive does the same almost three times faster...
>
> --
> [WBR], Arcade.
>