Re: CPU load due to IP networking

From: Unruh (unruh-spam_at_physics.ubc.ca)
Date: 06/22/05 

Date: 22 Jun 2005 00:50:20 GMT

"jbl" <levinjb@gmail.com> writes:

>I've been looking for some information on the web, in white papers and
>even on Usenet, but if it exists I can't seem to put together a search
>that finds it. I'm asking here if anyone knows of something along
>these lines and can point me to it.

>I'm looking for some data on the approximate resource cost,
>particularly CPU usage cost, of doing networking in a typical system,
>in particular a Unix-like system (linux is a suitable example) and
>vxworks (hence the crossposting).

This is an extremely ill defined question. It will depend on exactly how
the driver is written, how the driver is accessed by the software, etc.

>I'm not looking for bandwidth / capacity type data (e.g., N kpkts/sec
>or M MB/sec); these measures are fairly common and there are lots of
>examples on the web. Rather I'm looking for an approximate cycle or
>instruction count list, like this: I'd like to know that the CPU will
>expend A instructions (or cycles) per IP packet in, B cycles per IP
>packet out, C cycles per TCP packet in, D cycles per TCP packet out,
>etc.; and T cycles per connection per second, and U cycles per second
>for background processing, etc. Then using these numbers loosely as
>rules of thumb, and given a traffic model and a CPU of a certain type
>and speed, I could compute a rough estimate of what portion of the CPU
>capacity would be consumed by networking activities. I'd also like to
>include not only TCP/IP but UDP and some other router-like protocols
>(e.g. BGP or OSPF routing) and layer 2 activity (such as implied by
>ethernet connections.

>I hope it's clear enough what kind of data I'm looking for, and that I
>only need rough numbers. If anyone knows of something of this sort
>that's been published, for any operating system, actually, I'd
>appreciate a pointer.

The numbers you are liable to get will be so rough that you could guess
them just as profitably.

Maybe if y ou told us the problem you are trying to solve, you would get
better answers.

>Thanks / JBL

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