From: Andi Kleen <andi@firstfloor.org>
To: bert hubert <bert.hubert@netherlabs.nl>
Cc: netdev@vger.kernel.org
Subject: Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?
Date: 20 Feb 2007 11:50:13 +0100 [thread overview]
Message-ID: <p73d545drx6.fsf@bingen.suse.de> (raw)
In-Reply-To: <20070219231447.GA4400@outpost.ds9a.nl>
bert hubert <bert.hubert@netherlabs.nl> writes:
> Hi people,
>
> I'm trying to save people the cost of buying extra servers by making
> PowerDNS (GPL) ever faster, but I've hit a rather fundamental problem.
>
> Linux 2.6.20-rc4 appears to take 4 microseconds on my P4 3GHz for a
> non-blocking UDPv4 recvfrom() call, both on loopback and ethernet.
P4s are pretty slow at taking locks (or rather doing atomical operations)
and there are several of them in this path. You could try it with a UP
kernel. Actually hotunplugging the other virtual CPU should be sufficient
with recent kernels.
Also BTW RDTSC on P4 is not very accurate for small measurements
because it has a quite high overhead by itself, i would suggest
running it in a loop.
-Andi
next prev parent reply other threads:[~2007-02-20 9:50 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-19 23:14 nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz? bert hubert
2007-02-19 23:56 ` Stephen Hemminger
2007-02-20 8:04 ` bert hubert
2007-02-20 10:50 ` Andi Kleen [this message]
2007-02-20 16:27 ` all syscalls initially taking 4usec on a P4? " bert hubert
2007-02-20 16:41 ` Evgeniy Polyakov
2007-02-20 17:02 ` bert hubert
2007-02-20 17:11 ` Evgeniy Polyakov
2007-02-20 17:18 ` Evgeniy Polyakov
2007-02-21 11:06 ` Evgeniy Polyakov
2007-02-21 11:34 ` Andi Kleen
2007-02-20 18:42 ` Josef Sipek
2007-02-20 18:48 ` Evgeniy Polyakov
2007-02-20 19:33 ` bert hubert
2007-02-20 19:40 ` Benjamin LaHaise
2007-02-20 20:45 ` bert hubert
2007-02-20 21:02 ` Stephen Hemminger
2007-02-20 22:02 ` Rick Jones
2007-02-20 22:17 ` bert hubert
2007-02-20 22:22 ` Arjan van de Ven
2007-02-21 16:25 ` Chuck Ebbert
2007-02-20 22:46 ` Ian McDonald
2007-02-25 10:41 ` Pavel Machek
2007-02-25 17:06 ` Evgeniy Polyakov
2007-02-20 16:57 ` Eric Dumazet
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