poor ATA disk speed with ICH2

[Søren Schmidt]

Kevin Oberman wrote:
>>From: "Bjoern Koenig" <bkoenig at cs.tu-berlin.de>
>>Date: Wed, 8 Sep 2004 12:29:03 +0200
>>Sender: owner-freebsd-current at freebsd.org
>>
>>Hello,
>>
>>first time I installed a beta of FreeBSD 5.3 I noticed very poor disk =
>>speed.
>>I built a kernel without this whole debugging stuff; but it remains bad. =
>>I
>>supposed that this issue depends on further debugging features which I
>>didn't know. So I waited until UPDATING told that debugging options are
>>removed from kernel and userland. Now I built a new kernel again and the
>>disk speed is still unacceptable. Is there any further debugging option?
>>
>>Some facts:
>>
>>FreeBSD 5.3-BETA3 without any debugging:
>>	per char write: 13.78 MB/s (32.7% CPU usage)
>>	block write: 13.97 MB/s (12.8%)
>>	per char read: 22.31 MB/s (45.2%)
>>	block read: 37.44 MB/s (14.8%)
>>
>>FreeBSD 4.10-STABLE:
>>	per char write: 37.29 MB/s (75.7%)
>>	block write: 36.91 MB/s (28.7%)
>>	per char read: 38.53 MB/s (80.4%)
>>	block read: 37.45 MB/s (10.9%)
>>
>>(tested with bonnie, atacontrol shows UDMA100 both)
>>
>>Controller: Intel 82801BA (ICH2)
>>Hard disk: Seagate ST380021A
> 
> 
> I had previously reported this. I did some testing with the assistance
> of Robert Watson and it appears that the issue is ATA. The thread had a
> subject of "Disk performance under CURRENT" and was back in May.
> 
> I plotted out the times for various sizes of I/O and
> the only real issue was with write. The per character speed should
> increase fairly quickly with increased I/O size and did for V4 and for
> reads. For writes, it started the same for short writes as these tend to
> be CPU bound. But, for longer writes, the increase in speed is MUCH less
> than it was with V4 write or for reads and throughput tops out at
> between 16 and 32KB transfers at something far below what I saw in V4.
> 
> I was also hearing a LOT of disk seek operations that did not seem
> appropriate to me. (I did the testing with dd(1) in single-user mode.)
> 
> FWIW, I did my tests on an IBM T30 which is a P4 at 1.8 GHz with ICH3
> support chips.
> 
> Looking back at the history in my e-mail archive, I'm not certain that
> sos@ was copied. Ouch! Mea culpa!

I fixed a chip setup problem on the ICH* chips some days ago, its has 
been committed to RELENG_5 as well. However it would normally be 
harmless if the BIOS has set the mode (which it normally does).

Besides that, I know of no problems performance wise. Disk seek 
operations during sequential access suggests that there is something 
else going on simultanious to the test as the driver doesn't issue seeks 
without being asked to from the system.

-Søren