From owner-freebsd-net@FreeBSD.ORG  Wed Apr 29 07:30:41 2015
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 57FD8FAA;
 Wed, 29 Apr 2015 07:30:41 +0000 (UTC)
Received: from kerio.tuxis.nl (alcyone.saas.tuxis.net [31.3.111.19])
 (using TLSv1.1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id B739016C1;
 Wed, 29 Apr 2015 07:30:39 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=tuxis.nl; s=mail;
 h=from:subject:date:message-id:to:cc:mime-version:content-type:
 content-transfer-encoding:in-reply-to:references;
 bh=/9G5XxzKWELeo+I+7Y0pFQQmIraoAli5Il6LEYnjnTY=;
 b=R6/FC0hm/7dKCdVwvT4/ldYU3laEj0Tcksu3tHBtQqSTVi7Zdae0INYpuhe2ytVbefS1xkwhZz1Y1
 ltG8mWZx38NeKJvcgbkbzbRcdcyo0RcZimGW4b0wYb2sNXd1Hl9adbVLOP8lMB4pDmVwegnzuE0ZVn
 5O1pKvGWNmRxk1eO8pEwX/QYq0pjzyaXvxO924q5jTFo5ZLxdGSYZ0XvQkpMWja9dKjlR94AphYNHt
 esq45Lw4EVJQkwibvHNEcp53B49eUbWFJG1akUq6CBE3sqmrqQZQuT+01GnQ9lJhXbQ+uxCzFtiuPc
 xKYI3fTToTQO0bYyxWHzwBEWiebuxfA==
X-Footer: dHV4aXMubmw=
Received: from [31.3.104.222] ([31.3.104.222])
 (authenticated user mark@tuxis.nl)
 by kerio.tuxis.nl (Kerio Connect 8.5.0 beta 2)
 (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128 bits));
 Wed, 29 Apr 2015 09:30:34 +0200
Message-ID: <5540889A.5030904@tuxis.nl>
Date: Wed, 29 Apr 2015 09:30:34 +0200
From: Mark Schouten <mark@tuxis.nl>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
 rv:31.0) Gecko/20100101 Icedove/31.6.0
MIME-Version: 1.0
To: Rick Macklem <rmacklem@uoguelph.ca>
CC: freebsd-net@FreeBSD.org, Garrett Wollman <wollman@freebsd.org>
Subject: Re: Frequent hickups on the networking layer
References: <137094161.27589033.1430255162390.JavaMail.root@uoguelph.ca>
In-Reply-To: <137094161.27589033.1430255162390.JavaMail.root@uoguelph.ca>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.20
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: Wed, 29 Apr 2015 07:30:41 -0000

Hi,

On 04/28/2015 11:06 PM, Rick Macklem wrote:
> There have been email list threads discussing how allocating 9K jumbo
> mbufs will fragment the KVM (kernel virtual memory) used for mbuf
> cluster allocation and cause grief. If your
> net device driver is one that allocates 9K jumbo mbufs for receive
> instead of using a list of smaller mbuf clusters, I'd guess this is
> what is biting you.

I'm not really (or really not) comfortable with hacking and recompiling 
stuff. I'd rather not change anything in the kernel. So would it help in 
my case to lower my MTU from 9000 to 4000? If I understand correctly, 
this would need to allocate chunks of 4k, which is far more logical from 
a memory point of view?


Mark