From owner-freebsd-net@FreeBSD.ORG  Sat Mar 22 20:38:15 2014
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: net@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 67615740;
 Sat, 22 Mar 2014 20:38:15 +0000 (UTC)
Received: from mail-qc0-x231.google.com (mail-qc0-x231.google.com
 [IPv6:2607:f8b0:400d:c01::231])
 (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id 17248387;
 Sat, 22 Mar 2014 20:38:15 +0000 (UTC)
Received: by mail-qc0-f177.google.com with SMTP id w7so4311015qcr.22
 for <multiple recipients>; Sat, 22 Mar 2014 13:38:13 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:sender:in-reply-to:references:date:message-id:subject
 :from:to:cc:content-type;
 bh=ayWtcgYfUXQgprM/iLR+2pBjNa/HWFfra1EIImYVp+0=;
 b=eQ4d0bBX4I1Facnaqxda1wbRcJ68MM+IIKYuvv/Vwo8Ni9YAp6ClqyJYgBqul/qlDw
 YbocsmAtXtEKqglkvoRpe6qwvQk6vXh0ogSm49CAzwGBwZQGyLqYfwYLpNOmF2CSakm6
 Y72bjU77ZxWc+Q8QtokvV0fnW1NpCAaa4qYWH2BY1cxYcJZdkg/MMbNOzYfL9OzBgVdl
 FRZVeHKWCpBYIGPtSSXNWmCmNEcyrHB55v7upVm8GBDwh7rNqAZ6edf4EsxJXAaimB1q
 AEPJu5V7Ojg1auI5H7GVY0ncKwukXcf95PCdioJWASK34URH2s8vfMhJ2EaTroD1Oegn
 BLjQ==
MIME-Version: 1.0
X-Received: by 10.224.80.134 with SMTP id t6mr65675203qak.34.1395520693685;
 Sat, 22 Mar 2014 13:38:13 -0700 (PDT)
Sender: adrian.chadd@gmail.com
Received: by 10.224.8.137 with HTTP; Sat, 22 Mar 2014 13:38:13 -0700 (PDT)
In-Reply-To: <20140322182852.GW1499@glebius.int.ru>
References: <532817F5.8010505@oktetlabs.ru> <20140318132440.GG1499@FreeBSD.org>
 <532D62F8.4080103@oktetlabs.ru>
 <20140322182852.GW1499@glebius.int.ru>
Date: Sat, 22 Mar 2014 13:38:13 -0700
X-Google-Sender-Auth: JYCjo42TT6ynuee3GuFRy85_PNk
Message-ID: <CAJ-VmokJQpeNbSudQDH8_6DmwoCW1zON=02uFVPWTDpCPJR=yQ@mail.gmail.com>
Subject: Re: [PATCH 2/6] sfxge: limit software Tx queue size
From: Adrian Chadd <adrian@freebsd.org>
To: Gleb Smirnoff <glebius@freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1
Cc: "net@freebsd.org" <net@freebsd.org>,
 Andrew Rybchenko <Andrew.Rybchenko@oktetlabs.ru>
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net/>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
 <mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 22 Mar 2014 20:38:15 -0000

> Btw, there are some opinions that with modern cards any software
> queing is a bad idea. Driver should simply hold as much as hardware
> tx ring can hold. There is no yet stable decision about this, just
> thoughts floating around.

The drbr queue gives the driver the ability to source packets from
non-local cores for each TX queue.

Ie, it can place things into each hardware ring without having to grab
any locks to do so, and the TX can be initiated from the correct ring
if needs be.

So, it's not just doing "software queueing." -)


-a