i386/71761: disk write operations too slow (probably DMA problems with ICH2)

[Björn König]

>Number:         71761
>Category:       i386
>Synopsis:       disk write operations too slow (probably DMA problems with ICH2)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Sep 15 11:20:20 GMT 2004
>Closed-Date:
>Last-Modified:
>Originator:     Björn König
>Release:        FreeBSD 5.3-BETA4
>Organization:
>Environment:
FreeBSD alpha.local 5.3-BETA4 FreeBSD 5.3-BETA4 #0: Mon Sep 13 15:39:18 UTC 2004     bkoenig at hoppel.local:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
    Disk write speed since 5.3 ist too low.
37 MB/s are expected (5.2.1). I get around 13 MB/s
with 5.3-BETA. atacontrol shows already UDMA100, but if
I set UDMA100 explicitly again, then I get 25 MB/s;
it's still too slow.

It's not a hardware failure, because with 5.2.1
it still works perfectly. Mainboard is an Asus
TUSL2-C (i815EP) with ICH2 controller.

>How-To-Repeat:
dd if=/dev/zero of=<filename> bs=4096 count=262144
writes 1G of data and shows the average throughput.

>Fix:
      
>Release-Note:
>Audit-Trail:
>Unformatted: