netdev - Re: Strange packet drops with heavy firewalling

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Date:	Mon, 12 Apr 2010 16:44:39 +0200
From:	Benny Lyne Amorsen <benny@...rsen.dk>
To:	zhigang gong <zhigang.gong@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: Strange packet drops with heavy firewalling

man, 12 04 2010 kl. 16:16 +0800, skrev zhigang gong:

> How do you know the per CPU usage data, by oprofile? I'm just a little
> surprised with the result, as it shows your new core is running 10x
> faster than your old core :). 

Well the old server had only two CPU's plus hyperthreading, and the
CPU's were Pentium-4-based. Add a slow memory bus to that and you have a
fairly slow system. It's almost 5 years old, so Moore's law says 2**3
increase in number of transistors...

In about the same time frame Linux has gone from being able to fill
1Gbps ethernet to being able to fill 10Gbps ethernet 

> What's the average packet size?

I asked the switch (I can't find a handy equivalent to ifstat which
counts packets instead of bytes). The 5 minute average packet sizes seem
to vary in the range 450 to 550 bytes.

> If your packet size is 64 bytes, then the pps(packet per second) rate
> should be about 585Kpps. As I know, this value is almost the best
> result when the standard linux kernel is processing the networking
> traffic with a normal 1Gb ethernet card (without multi-queue support)
> on a intel box. If it is the case, to buy a better ethernet card with
> multi-queue support should be a good choice. Otherwise, it may not
> help. 

I am far from that, perhaps 1/10th of that. I do a lot more processing
on at least some of the packets though (the ones starting new flows).

/Benny

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