Difference between 6.2 and 7.0 Adaptec 39320D - 7.0 performing less

Scott Long scottl at samsco.org
Tue Apr 17 14:45:41 UTC 2007

Gelsema, P (Patrick) - FreeBSD wrote:
> On Tue, April 17, 2007 01:03, Kris Kennaway wrote:
>> On Mon, Apr 16, 2007 at 10:47:24PM +0200, Gelsema, P (Patrick) wrote:
>>> Goodevening lists,
>>> I am toying with Freebsd 7 to see if it will and how it runs on my new
>>> Asus
>>> M2N mainboard. One of the things I noticed is that when running
>>> 7.0-Current-200704 the throughput of the SCSI drive seems halved. When
>>> running 6.2 throughput is doubled/normal.
>>> Throughput is measured with the following command.
>>> dd if=/dev/zero of=/usr/test
>>> where /usr resides on da0s1f
>>> On 7.0 I get about 33MB/sec
>>> On 6.2 I get about 69Mb/sec
>>> I did not make any changes, installation is fresh from CD with Minimal
>>> as
>>> distribution.
>> Apparently you weren't paying attention during boot, because 7.0 ships
>> with heavy debugging options enabled, and tells you about it up front:
>>      "WARNING: WITNESS option enabled, expect reduced performance.\n";
>> Recompile your kernel with debugging options disabled before making
>> performance comparisons.
>> Kris
> Ok, what you are saying makes sense. I did see the warnings and the bits
> in the kernel config. The thing that triggered me was that when paying
> attention during boot the SCSI Disk was detected as only 160.00MB/s
> instead of the expected 320.00MB/s. The detection of devices is not
> subject to debugging, is it?
> Excerpts from log.
> Freebsd 7
> da0: <SEAGATE ST336753LW HPS2> Fixed Direct Access SCSI-3 device
> da0: 160.000MB/s transfers (80.000MHz DT, offset 63, 16 bit)
> da0: Command Queueing Enabled
> Freebsd 6.2
> da0: <SEAGATE ST336753LW HPS2> Fixed Direct Access SCSI-3 device
> da0: 320.000MB/s transfers (160.000MHz DT, offset 63, 16 bit), Tagged
> Queueing Enabled
> Thanks,

The 39320D is a finicky card.  I don't recall putting in the code that
would downshift the speed like this, but it wouldn't surprise me if it
is a side effect of the system going slower.  Anyways, it sounds like
you're a good candidate/victim for the MPSAFE locking changes that I
just made to the SCSI layer and the ahc/ahd drivers.  Would you mind
testing it out (just update to the latest 7-CURRENT sources) and let me
know how it works for you?


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