linux-kernel - Re: loaded router, excessive getnstimeofday in oprofile

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Message-ID: <20080827223952.GE26610@one.firstfloor.org>
Date:	Thu, 28 Aug 2008 00:39:52 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	David Miller <davem@...emloft.net>
Cc:	andi@...stfloor.org, rick.jones2@...com, johnpol@....mipt.ru,
	dada1@...mosbay.com, denys@...p.net.lb, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: loaded router, excessive getnstimeofday in oprofile

On Wed, Aug 27, 2008 at 03:18:24PM -0700, David Miller wrote:
> From: Andi Kleen <andi@...stfloor.org>
> Date: Wed, 27 Aug 2008 18:27:35 +0200
> 
> > > Those banks really want to crank down on latency - to the point they 
> > > start disabling interrupt coalescing.  I bet they'd toss anything out 
> > > they could to shave another microsecond.
> > 
> > This change would actually likely lower their latency.
> 
> They want the timestamps, but they want it to match when the packet
> arrived at their system as closely as is reasonably possible.

Then they should use hardware time stamps which are increasingly 
available (e.g. current Intel e1000 design has them and I expect
others too). 

-Andi

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