ATA disk performance (ICH2 controller), some tests and comparison with Linux 2.6.5

Hello,

I post some tests about the performance of my ATA disk (which is not 
very spectacular under FREEBSD 6.0).
Notice that the write performance improves considerably after 
reinitializing the ATA channel. I've given a comparison with
the performance under Linux (kernel 2.6.5) which is far better (with 
identical HW of course, since I can boot
both Linux 2.6.5 and FreeBSD current). Can someone help me to explain 
this facts or tell me what I am doing wrong?

Kind regards, Mauro

i) System & hardware

foo# uname -a
FreeBSD foo.bar.com 6.0-CURRENT FreeBSD 6.0-CURRENT #0: Sat Sep 25 
17:54:29 CEST 2004     
triulzi_at_foo.bar.com:/usr/src/sys/i386/compile/MYKERNEL  i386

source tree actualized and built today, all debugging options disabled.

My HW:

foo# pciconf -v -l
(...)
atapci0_at_pci0:31:1:      class=0x010180 card=0x01451028 chip=0x244b8086 
rev=0x04 hdr=0x00
    vendor   = 'Intel Corporation'
    device   = '82801BA (ICH2) UltraATA/100 IDE Controller'
    class    = mass storage
    subclass = ATA
(...)

Mode (before reinitialization, see below)

foo# atacontrol mode 0
Master = UDMA100
Slave  = BIOSPIO

Kernel parameters (also before reinitialization):
foo# sysctl hw.ata.

hw.ata.ata_dma: 1
hw.ata.wc: 1
hw.ata.atapi_dma: 1

ii) TESTS: all tests with 512B blocks read/write

a) under FreeBSD

Write test:

foo# date && dd if=/dev/zero of=deleteme.now count=1000000 && date
Sat Sep 25 22:04:02 CEST 2004
1000000+0 records in
1000000+0 records out
512000000 bytes transferred in 34.238161 secs (14954074 bytes/sec)
Sat Sep 25 22:04:36 CEST 2004

Read test:

foo# date && dd if=/dev/ad0s3g of=/dev/null count=1000000 && date
Sat Sep 25 22:08:13 CEST 2004
1000000+0 records in
1000000+0 records out
512000000 bytes transferred in 125.686697 secs (4073621 bytes/sec)
Sat Sep 25 22:10:18 CEST 2004

Reinitialize the ATA channel:

foo# atacontrol reinit 0
Master:  ad0 <IC35L060AVV207-0/V22OA63A> ATA/ATAPI revision 6
Slave:       no device present

Write test after reinitialization:

foo# date && dd if=/dev/zero of=deleteme.now count=1000000 && date
Sat Sep 25 22:12:30 CEST 2004
1000000+0 records in
1000000+0 records out
512000000 bytes transferred in 15.110452 secs (33883831 bytes/sec)
Sat Sep 25 22:12:45 CEST 2004

(about twice faster!! Why?)

Read test after reinitialization:

foo# date && dd if=/dev/ad0s3f of=/dev/null count=1000000 && date
Sat Sep 25 22:14:51 CEST 2004
1000000+0 records in
1000000+0 records out
512000000 bytes transferred in 125.860301 secs (4068002 bytes/sec)
Sat Sep 25 22:16:56 CEST 2004

(read from another device to avoid caching effects)

Reinitialization of the ATA channel has effects only on write performance.
Read performance is very bad.

b) Now the same under Linux (kernel 2.6.5)

Write performance

linux:/usr # date && dd if=/dev/zero of=deleteme.now count=1000000 && date
Sat Sep 25 21:38:30 CEST 2004
1000000+0 records in
1000000+0 records out
Sat Sep 25 21:38:35 CEST 2004

deleteme.now is about 488 MB, rate about 100 MB/sec!!

Read performance

linux:/usr # date && dd if=/dev/hda11 of=/dev/null count=1000000 && date
Sat Sep 25 21:41:31 CEST 2004
1000000+0 records in
1000000+0 records out
Sat Sep 25 21:41:43 CEST 2004

that is about 40MB/sec!! (/dev/hda11 read for the first time, to avoid 
caching).

Kind regards,
Mauro