Messages in this thread | | | From | Greg Lindahl <> | Subject | Re: http://www.nfr.net/nfr/mail-archive/nfr-users/1999/Feb/0110.html | Date | Fri, 23 Apr 1999 14:24:23 -0400 (EDT) |
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> > The bsd machines were sniffing 45,000 packets per second. Linux -- in > > the default configuration -- can't even receive 45,000 packets per > > second, because of the default setting of > > /proc/sys/net/core/netdev_max_backlog. > > I've benched a Linux box with the standard settings doing over 55,000 packets > per second _routing_ not just receiving.
But you had a tail-wind. I take it that the bottom half can execute more than 100x a second if the machine is otherwise idle. But if anything comes along and uses a whole timeslice, the backlog queue fills (default size 300) and you start dropping packets on the floor. Yes? No?
And routing is fairly efficient; it's all in the kernel, at least. Sniffing, on the other hand, consumes a fair bit of extra CPU time getting the data up to the user process and consuming it.
> The fun with NFR isnt the device backlog, its that BSD has a hack built into > it basically solely for sniffing tools to use, and Linux doesn't.
That may be the key to getting to *really* high packet rates. But Linux, pin their test, slowed down as the packet rate increased. That's what made me suspect the backlog. But it's just a guess.
-- g
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