Effects of turning off MSI-X

[stvboyle]

First, I'm running pfSense 2.0.1, amd64.  The systems have 2 bce interfaces and 2 igb interfaces.  The igb interfaces handle the bulk of the traffic and we use one of the bce interfaces for Carp.  On the bce interfaces that are used for Carp, I see inbound Discards.  I've been looking at this doc:
http://doc.pfsense.org/index.php/Tuning_and_Troubleshooting_Network_Cards

One of the suggestions in the doc for bce cards is:
hw.pci.enable_msix=0

My question is, what effect does that have exactly?  Does that causes all the NICs to stop using interrupts and start polling?  I'm looking to solve the bce problem without affecting the igb interfaces.

Thanks!!

[jimp]

No, it actually makes the NICs use interrupts instead of using MSI/MSI-X

Polling is entirely different.

http://en.wikipedia.org/wiki/Message_Signaled_Interrupts

[stvboyle]

Cool, thanks.  Was not sure if that meant hardware interrupts or no interrupts.