From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Graf Subject: Re: [PATCH] sctp: Reducing rwnd by sizeof(struct sk_buff) for each CHUNK is too aggressive Date: Fri, 24 Jun 2011 11:53:16 -0400 Message-ID: <20110624155316.GD9222@canuck.infradead.org> References: <20110624101535.GB9222@canuck.infradead.org> <4E0495C3.30102@hp.com> <20110624144251.GC9222@canuck.infradead.org> <4E04AB67.1040407@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Sridhar Samudrala , linux-sctp@vger.kernel.org, netdev@vger.kernel.org To: Vladislav Yasevich Return-path: Received: from merlin.infradead.org ([205.233.59.134]:59962 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754358Ab1FXPxT (ORCPT ); Fri, 24 Jun 2011 11:53:19 -0400 Content-Disposition: inline In-Reply-To: <4E04AB67.1040407@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Jun 24, 2011 at 11:21:11AM -0400, Vladislav Yasevich wrote: > First, let me state that I mis-understood what the patch is attempting to do. > Looking again, I understand this a little better, but still have reservations. This explains a lot :) > If we treat the window as strictly available data, then we may end up sending a lot more traffic > then the window can take thus causing us to enter 0 window probe and potential retransmission > issues that will trigger congestion control. > We'd like to avoid that so we put some overhead into our computations. It may not be ideal > since we do this on a per-chunk basis. It could probably be done on per-packet basis instead. > This way, we'll essentially over-estimate but under-subscribe our current view of the peers > window. So in one shot, we are not going to over-fill it and will get an updated view next > time the SACK arrives. I will update my patch to include a per packet overhead and also fix the retransmission rwnd reopening to do the same.