[Gllug] Poor disk performance - help

[Alain Williams]

On Mon, Mar 22, 2004 at 10:06:38AM +0000, Doug Winter wrote:
> On Sun 21 Mar Alain Williams wrote:
> > I have just replaced my motherboard & CPU - but disk I/O is abysmal.
> > I have AMD Athlon XP 3000+ running at 2166 MHz, I have 1G ddr 333MHz
> > RAM.  Soltek motherboard (SLKT600-RL).  I have IDE 2 disks & 2 CDs.
> > 
> > Machine seems OK except that disk i/o is slooow and uses vast amounts
> > of CPU, I first noticed it when a ftp from a local machine was
> > ~2Mbyte/sec with 50->100% cpu, I would expect ~10MB/sec.
> 
> Oddly enough I've just put a new AMD machine together, although with the
> Chaintech mobo, so this may or may not be the same for you (the
> chaintech uses the nvidia nforce3 chipset whereas the soltek uses the
> VIA KT600).
> 
> I found that my APIC isn't properly supported in either 2.4 or 2.6, and
> needs to be disabled.  I had all sorts of interrupt grief (which is what
> it sounds like you've got), but disabling the APIC fixed it.
> 
> Boot with enable="noapic" in your lilo.conf and see if that solves your
> problem.  Obviously you want to be using the APIC if possible, but at
> least this narrows down the problem.

No, my problem is because the RedHat kernel doesn't recognise the isa bridge (the south bridge)
and so disables DMA -- it even prints a boot time message to say so.

It is a vt8235 (or perhaps vt8237 - I'm not at home at the moment), a glance at the source shows that
it is recognised by the 2.4 kernels, but not the current RedHat ones - I'll roll my own & should be OK.

It is interesting that performance is kind of OK until I hit the disk hard.

Oh, the excitement of bleeding edge kit !

-- 
Alain Williams

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