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In-Reply-To: <slrnj25jkk.r6m.vadim_nuclight@kernblitz.nuclight.avtf.net>
References: <20110714154457.GI70776@FreeBSD.org>
	<slrnj25jkk.r6m.vadim_nuclight@kernblitz.nuclight.avtf.net>
Date: Sun, 17 Jul 2011 10:15:05 -0400
Message-ID: <CAFMmRNxbw=akdBSn7jZi_S3iuk7GV7-P8naNPvSiXcs-SyCkKQ@mail.gmail.com>
From: Ryan Stone <rysto32@gmail.com>
To: vadim_nuclight@mail.ru
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Cc: freebsd-net@freebsd.org
Subject: Re: m_pkthdr.rcvif dangling pointer problem
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On Sun, Jul 17, 2011 at 7:59 AM, Vadim Goncharov <vadim_nuclight@mail.ru> wrote:
> Ways to improve are to be found from this starting point. However,
> are that +2 atomic ops per packet really so expensive? How many of
> atomic ops are already on that path? Any measures?

On high-performance multiqueue NICs, those two atomic ops are pretty
well guaranteed to be contended every time.  It's a scalability
nightmare.