I/O Bottlenecks on PCI bus?

[Chuck Forsberg WA7KGX]

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)?

[Michael Cronenworth]

-------- Original Message --------
Subject: I/O Bottlenecks on PCI bus?
From: Chuck Forsberg WA7KGX N2469R 
To: Fedora Test List 
Date: 12/22/2008 06:52 AM
> Is the PCI bus that easy to saturate??
> Any inexpensive ways to relieve the bottleneck(s)?

It depends on your motherboard, CPU, and network card. Some cheap 
motherboards produce well below average performance.

P.S. This doesn't seem like a fedora-test-list discussion topic.

[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