From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: [PATCH] sendfile() and UDP socket Date: Tue, 23 Sep 2008 11:07:58 +0400 Message-ID: <20080923070758.GD25231@2ka.mipt.ru> References: <20080922070425.GA14572@2ka.mipt.ru> <20080923062709.GA7886@2ka.mipt.ru> <20080923070133.GB26836@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem@davemloft.net, johaahn@gmail.com, netdev@vger.kernel.org To: Herbert Xu Return-path: Received: from relay.2ka.mipt.ru ([194.85.80.65]:44934 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753092AbYIWHI6 (ORCPT ); Tue, 23 Sep 2008 03:08:58 -0400 Content-Disposition: inline In-Reply-To: <20080923070133.GB26836@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Sep 23, 2008 at 03:01:33PM +0800, Herbert Xu (herbert@gondor.apana.org.au) wrote: > Yes but bulk transfers over UDP is a bad idea regardless of how > slow your bus is :) It still deserves living if it is not highly priority traffic like video dataflow. > So what application needs this? Johann did not show his exact usage scenario, but from what I got I concluded, that it is kind of a video sensor (or some other data which is allowed to be lost), which has to add a header to the frame and submit it to the network without any copy because of hardware limitation for the memory bus. Sensor can put data via DMA to the needed location. His first (and parallel to this one) idea was to extend packet socket to allow send of the mapped data. I proposed to do the same with sendfile, i.e. dma data to the mapped area of some file in the ramdisk, add header, do it for multiple frames and then send given file using sendfile(). -- Evgeniy Polyakov