Re: Linux 2.6.22-rc2

Stephen Hemminger
2007-05-22T17:19:56Z

On Mon, 21 May 2007 22:04:26 -0700 (PDT)
Linus Torvalds <torvalds@linux-foundation.org> wrote:

>
>
> On Mon, 21 May 2007, Stephen Hemminger wrote:
> >
> > AHCI on this motherboard doesn't seem to use MSI. The problems occur
> > even if I boot with nomsi.
>
> Have you tried playing with PCI latency counters etc?
>
> Maybe the SATA/AHCI thing is better at saturating the bus, and the sky2
> hardware gets upset if it has overlong DMA access latencies due to some
> other controller keeping the bus busy with a long burst access?
>
> I can't really see that being a real problem in this day and age of PCI-X
> etc, but it _used_ to be a possible issue a decade ago. Maybe you've found
> a case where it matters even on modern hardware? We occasionally used to
> set the PCI latency timer to make people happy.
>
> (Not that I'm convinced it even has any semantic meaning on a modern PCI
> system..)
>
> Linus

The device in question is PCI Express, and the latency has no meaning (at
least in vendor spec).

--
Stephen Hemminger <shemminger@linux-foundation.org>