I/O Bottlenecks on PCI bus?

[Gilboa Davara]

On Mon, 2008-12-22 at 04:52 -0800, Chuck Forsberg WA7KGX N2469R wrote:
> Comcast recently doubled my download speed to something
> close to 12 mbit/sec.    Now I/O bottlenecks are becoming apparent.
> 
> My server has  PCI bus controller cards for two hard drives
> and the external network. The local net and the other drives
> use motherboard connectors.  Processor is an AMD 6000+
> dual core with 8GB memory.
> 
> I can run a compute bound process such as Dhrystone with
> no noticeable effect on download speed.   However, an
> i/o intensive progrma such as quickpar or unrar  accessing
> data on local disks served by the PCI interface board
> slows incoming data to hafe or a third of normal.
> 
> Is the PCI bus that easy to saturate??
> Any inexpensive ways to relieve the bottleneck(s)?

Chuck,

I doubt that you are event close to congesting your PCI-E bridge and/or
HT links.

Even you are using a PCI network card (instead of say, onboard GbE NIC
and/or PCI-E NIC), you are still capped at ~130MB/s (real-life 100MB/s).

To put things in perspective, on a somewhat slower machine (Dual single
core Opteron 252), a certain software that I'm using is processing
>1.8Gbps (~225MB/s) coming down two GbE links. (Sitting on the PCI-X
bus).

Having said all that, what protocol are you using to connect to your
ISP? L2TP? PPTP? What's your CPU load during normal browsing?

- Gilboa