Re: mfi driver performance

On Thursday, September 13, 2012 4:48:20 pm matt wrote:
> On 09/13/12 13:13, Garrett Cooper wrote:
> > On Thu, Sep 13, 2012 at 12:54 PM, matt <sendtomatt_at_gmail.com> wrote:
> >> On 09/10/12 19:31, Garrett Cooper wrote:
> > ...
> >
> >> It seems hw.mfi.max_cmds is read only. The performance is pretty close to
> >> expected with no nvram or bbu on this card and commodity disks from 1.5
> >> years ago, as far as I'm concerned. I'd love better write performance, 
but
> >> it's probably being held back by the single platter in the mirror when it 
is
> >> writing far from its edge.
> > Try loader.conf:
> >
> > $ grep -r hw.mfi.max_cmds /sys/dev/mfi/
> > /sys/dev/mfi/mfi.c:TUNABLE_INT("hw.mfi.max_cmds", &mfi_max_cmds);
> >
> > Cheers,
> > -Garrett
> $ cat /usr/src/sys/dev/mfi/*.c | fgrep 'max_cmds'
> static int    mfi_max_cmds = 128;
> TUNABLE_INT("hw.mfi.max_cmds", &mfi_max_cmds);
> SYSCTL_INT(_hw_mfi, OID_AUTO, max_cmds, CTLFLAG_RD, &mfi_max_cmds,
>     ncmds = MIN(mfi_max_cmds, sc->mfi_max_fw_cmds);
> 
> Definitely a loader tunable, thanks. I'll try increasing and decreasing
> the value and running bonnie again...Still not sure whether I'm getting
> 3gb/s and 6gb/s negotiation with my drives. MPS correctly reported da
> devices with 600mb/s and 300mb/s transfers where appropriate. mfiutil
> doesn't seem to know, and mfip devices appear as 150mb/s. No transfer
> speed message when mfisyspd devices attach.

Mess with mfi_max_cmds at your own risk.  The limit was added to work around
broken mfi(4) firmware revisions that would lock up when the entire command
queue (256) was used.  Just a suggestion to be cautious.  It is probably
safe to use more than 128, but I would be wary of using all of the slots on 
your adapter.  (A verbose boost will show you the number of command slots your
firmware supports.)

-- 
John Baldwin