poor ATA disk speed with ICH2

Kevin Oberman oberman at es.net
Thu Sep 9 10:14:08 PDT 2004

> 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!
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634

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