Intel says that this utilization is normal, but my clients don't like that high of an "idle" utilization.
Articles and Tips: qna
01 Sep 1999
Q.
Dear Ab-end: I have several NetWare 5 servers running an Intel Server NIC in polling mode. The server's new idle utilization is 33%. Intel says that this utilization is normal, but my clients don't like that high of an "idle" utilization. As a result, we switched to interrupt mode and the idle utilization went back to 0%. How does this all work?
A NIC in Time
A.
Dear NIC: According to former Novell employee Scott Lemon, "The benefit of polled mode is when there is a lot of traffic, not when the server is idle. The background utilization is caused by the polling, but it is well worth it when traffic picks up and the server gets busy. Interrupts are very costly to handle since each one forces an immediate context switch, and if they are occurring on every packet coming in, the server is constantly interrupted.
"With polled mode, the server can regularly check for incoming packets in an organized way, prepared for any required handling of registers or stack. It is much more efficient to the server. But I do understand the customer who wants their idle server to look idle. It's too bad our user base out there can't be properly educated to understand that our architecture would greatly benefit if they used polled mode. They would get a lot more headroom for busy times instead of topping out at 100% utilization as quickly.
"For the best performance, try to run the NIC in polled mode, but remember the driver does need to support it." (See also "A Discussion on Interrupts and NetWare" found in this issue of NetNotes.)
* Originally published in Novell AppNotes
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