From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757137AbZBFLLJ (ORCPT ); Fri, 6 Feb 2009 06:11:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754451AbZBFLK4 (ORCPT ); Fri, 6 Feb 2009 06:10:56 -0500 Received: from 1wt.eu ([62.212.114.60]:2070 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754437AbZBFLK4 (ORCPT ); Fri, 6 Feb 2009 06:10:56 -0500 Date: Fri, 6 Feb 2009 12:10:15 +0100 From: Willy Tarreau To: Jarek Poplawski Cc: Herbert Xu , David Miller , zbr@ioremap.net, dada1@cosmosbay.com, ben@zeus.com, mingo@elte.hu, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, jens.axboe@oracle.com Subject: Re: [PATCH v2] tcp: splice as many packets as possible at once Message-ID: <20090206111015.GD15159@1wt.eu> References: <20090202084358.GB4129@ff.dom.local> <20090202.235017.253437221.davem@davemloft.net> <20090203094108.GA4639@ff.dom.local> <20090205.235258.257422341.davem@davemloft.net> <20090206091034.GA4879@ff.dom.local> <20090206092326.GC6645@gondor.apana.org.au> <20090206095119.GC4879@ff.dom.local> <20090206102822.GB7175@gondor.apana.org.au> <20090206105807.GD4879@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090206105807.GD4879@ff.dom.local> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 06, 2009 at 10:58:07AM +0000, Jarek Poplawski wrote: > On Fri, Feb 06, 2009 at 09:28:22PM +1100, Herbert Xu wrote: > > On Fri, Feb 06, 2009 at 09:51:20AM +0000, Jarek Poplawski wrote: > > > > > > OK, but since there is not so much difference, and we need to waste > > > it in some cases anyway, plus handle it later some special way, I'm > > > a bit in doubt. > > > > Well the thing is cards that don't support SG on tx probably > > don't support jumbo frames either. > > ?? I mean this 128 byte chunk would be hard to reuse after copying > to skb->data, and if reused, we could miss this for some NICs on TX, > so the whole packed would need a copy. couldn't we stuff up to 32 128-byte chunks in a page and use a 32-bit map to indicate which slot is used and which one is free ? This would just be a matter of calling ffz() to find one spare place in a page. Also, that bitmap might serve as a refcount, because if it drops to zero, it means all slots are unused. And -1 means all slots are used. This would reduce wastage if wee need to allocate 128 bytes often. Willy