From owner-svn-src-all@FreeBSD.ORG  Wed Jun  4 02:52:19 2014
Return-Path: <owner-svn-src-all@FreeBSD.ORG>
Delivered-To: svn-src-all@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 42ECB4E4
 for <svn-src-all@freebsd.org>; Wed,  4 Jun 2014 02:52:19 +0000 (UTC)
Received: from cell.glebius.int.ru (glebius.int.ru [81.19.69.10])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client CN "cell.glebius.int.ru", Issuer "cell.glebius.int.ru" (not verified))
 by mx1.freebsd.org (Postfix) with ESMTPS id B50E42705
 for <svn-src-all@freebsd.org>; Wed,  4 Jun 2014 02:52:18 +0000 (UTC)
Received: from cell.glebius.int.ru (localhost [127.0.0.1])
 by cell.glebius.int.ru (8.14.8/8.14.8) with ESMTP id s542pW0T024467
 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);
 Wed, 4 Jun 2014 06:51:32 +0400 (MSK)
 (envelope-from glebius@FreeBSD.org)
Received: (from glebius@localhost)
 by cell.glebius.int.ru (8.14.8/8.14.8/Submit) id s542pWoA024466;
 Wed, 4 Jun 2014 06:51:32 +0400 (MSK)
 (envelope-from glebius@FreeBSD.org)
X-Authentication-Warning: cell.glebius.int.ru: glebius set sender to
 glebius@FreeBSD.org using -f
Date: Wed, 4 Jun 2014 06:51:32 +0400
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: David Chisnall <theraven@theravensnest.org>
Subject: Re: svn commit: r266974 - in head/sys: dev/dc dev/fxp dev/mii
 dev/netmap kern net
Message-ID: <20140604025132.GD50679@FreeBSD.org>
References: <201406021754.s52Hsd1B039620@svn.freebsd.org>
 <CAJ-VmonRqXrzrqQys_9s7-o8DFmOE_c_BZWupezm0i+W7E09vA@mail.gmail.com>
 <CAJ-VmonDJCLYWBPiz1ntFRm8aj4WQd5iHMKK0Wm3hcdjZmxghw@mail.gmail.com>
 <DA4CB2BA-A551-47A4-9E44-766FA29E2EF2@xcllnt.net>
 <20140603012939.GA2998@michelle.cdnetworks.com>
 <CAJ-Vmomt+HN7veD79a7h+v9P4R6LdhAJpRB79yjwGd3H+dSpow@mail.gmail.com>
 <D1E5E176-F7BD-4F13-8E09-6843038B162B@theravensnest.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <D1E5E176-F7BD-4F13-8E09-6843038B162B@theravensnest.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
Cc: Yong-Hyeon Pyun <pyunyh@gmail.com>, Adrian Chadd <adrian@FreeBSD.org>,
 Marcel Moolenaar <marcel@freebsd.org>,
 "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,
 Marcel Moolenaar <marcel@xcllnt.net>,
 "src-committers@freebsd.org" <src-committers@freebsd.org>,
 "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>
X-BeenThere: svn-src-all@freebsd.org
X-Mailman-Version: 2.1.18
Precedence: list
List-Id: "SVN commit messages for the entire src tree \(except for &quot;
 user&quot; and &quot; projects&quot; \)" <svn-src-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-all>,
 <mailto:svn-src-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-all/>
List-Post: <mailto:svn-src-all@freebsd.org>
List-Help: <mailto:svn-src-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-all>,
 <mailto:svn-src-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 04 Jun 2014 02:52:19 -0000

On Tue, Jun 03, 2014 at 06:05:50PM +0100, David Chisnall wrote:
D> On 3 Jun 2014, at 06:01, Adrian Chadd <adrian@FreeBSD.org> wrote:
D> 
D> > I wonder if in the short term we should just use inlines for now, at
D> > least so the methodization can get done without hurting people on
D> > ARM/MIPS.
D> 
D> It's probably worth thinking a bit more carefully about the KPI, since it's something we'll likely be stuck with for a long time...
D> 
D> If access to a particular field is on the hot path, and you're never going to want to do interposition, then the obvious thing to do is have a method that returns a pointer to the field so that you can cache it in the caller.  Some thought needs to be given there as to whether these things are _Atomic() qualified for when we (eventually) move to C11 for the kernel.

Yes, this is the plan. Some high performance drivers can cache pointers to
partial contents of an ifnet(9).

-- 
Totus tuus, Glebius.