netdev - Re: Multicast Routing Kernel option?

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Message-ID: <87tzdmxt6j.fsf@basil.nowhere.org>
Date:	Fri, 15 Aug 2008 16:13:24 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	imipak@...oo.com
Cc:	netdev@...r.kernel.org, Daniel Ng <daniel_ng11@...os.com>
Subject: Re: Multicast Routing Kernel option?

Jonathan Day <imipak@...oo.com> writes:

> They could, I guess, but context switches are expensive (think 20ms
> from kernel to user, and same in reverse)

40ms for a system call? That would be really horrible if it really
were that slow. Fortunately it's not. A Core2 (Merom) here can do a
very simple system call roundtrip (getppid()) in ~570 cycles, that is
at 2Ghz less than 300ns. You are roughly 5 orders of magnitude off.

-Andi
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