Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755488Ab0HXTuD (ORCPT ); Tue, 24 Aug 2010 15:50:03 -0400 Received: from smtp.srv.ualberta.ca ([129.128.5.19]:62998 "EHLO mail4.srv.ualberta.ca" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752803Ab0HXTuA (ORCPT ); Tue, 24 Aug 2010 15:50:00 -0400 Date: Tue, 24 Aug 2010 13:49:14 -0600 (Mountain Daylight Time) From: Marc Aurele La France To: Ben Hutchings cc: Stephen Hemminger , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, "David S. Miller" , Alexey Kuznetsov , "Pekka Savola (ipv6)" , James Morris , Hideaki YOSHIFUJI , Patrick McHardy Subject: Re: RFC: MTU for serving NFS on Infiniband In-Reply-To: <1282672647.2302.15.camel@achroite.uk.solarflarecom.com> Message-ID: References: <20100823080543.319143e3@nehalam> <1282672647.2302.15.camel@achroite.uk.solarflarecom.com> User-Agent: Alpine 2.00 (WNT 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2313 Lines: 45 On Tue, 24 Aug 2010, Ben Hutchings wrote: > On Tue, 2010-08-24 at 09:14 -0600, Marc Aurele La France wrote: >> On Mon, 23 Aug 2010, Stephen Hemminger wrote: >>> On Mon, 23 Aug 2010 08:44:37 -0600 (MDT) >>> Marc Aurele La France wrote: >>>> In regrouping for my next tack at this, I noticed that all stack traces go >>>> through ip_append_data(). This would be ipv6_append_data() in the IPv6 case. >>>> A _very_ rough draft that would have ip_append_data() temporarily drop down >>>> to a smaller fake MTU follows ... >>> Why doesn't NFS generate page size fragments? Does Infiniband or your >>> device not support this? Any thing that requires higher order allocation >>> is going to unstable under load. Let's fix the cause not the apply bandaid >>> solution to the symptom. >> From what I can tell, IP fragmentation is done centrally. > [...] > Stephen and I are not talking about IP fragmentation, but about the > ability to append 'fragments' to an skb rather than putting the entire > packet payload in a linear buffer. See > . Any payload has to either fit in the MTU, or has to be broken up into MTU-sized (or less) fragments, come hell or high water. That this is done centrally is a good thing. It is the "(or less)" part that I am working towards here. Marc. +----------------------------------+----------------------------------+ | Marc Aurele La France | work: 1-780-492-9310 | | Academic Information and | fax: 1-780-492-1729 | | Communications Technologies | email: tsi@ualberta.ca | | 352 General Services Building +----------------------------------+ | University of Alberta | | | Edmonton, Alberta | Standard disclaimers apply | | T6G 2H1 | | | CANADA | | +----------------------------------+----------------------------------+ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/