From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753218Ab0DZSNY (ORCPT ); Mon, 26 Apr 2010 14:13:24 -0400 Received: from kroah.org ([198.145.64.141]:40665 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752258Ab0DZSNW (ORCPT ); Mon, 26 Apr 2010 14:13:22 -0400 Date: Mon, 26 Apr 2010 11:11:52 -0700 From: Greg KH To: "B.Vinai Kumar" Cc: linux-kernel , linux-usb , usbip-devel@lists.sourceforge.net, Takahiro Hirofuchi Subject: Re: zero copy in usbip send and recieve path Message-ID: <20100426181152.GB23986@kroah.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 26, 2010 at 04:27:46PM +0530, B.Vinai Kumar wrote: > Hi All, > > I'am trying to implement zero copy in USBIP while sending / receiving > usbip packets. > > I started it with send path. The device which I used is mass storage. > I'am using linux kernel 2.6.15. 2.6.15 is _very_ old, and not supported by anyone. You might try this on a more modern kernel release, like 2.6.33 or newer. > After virtualization, once the file copy starts from device to pc each > usbip packet carries payload of 64K. > > I'am allocating this 64K buffer through __get_free_pages() (with order > 4) and assigning the buffer pointer to urb. After completion of URB > i'am trying to send this buffer page by page by using tcp_sendpage > instead of calling kernel_sendmsg(), this is to avoid copy which is > done in the TCP send path. > > By doing this way it is able to send the buffer successfully, but I'am > not finding the way to free this buffer. This copy continues until the > entire memory is consumed. After you are done with the memory, you need to explicitly free it, why can't you do that? > who will free this buffer? You need to. > 1) If i call free_pages for entire 64K right after tcp_sendpage (i.e > after sending all the pages, 64K). then observed > the Kernel panic. It is obvious that the tcp core is not yet finished its job. > > 2) TCP core is also not freeing these pages. > > This might be because, I allocated 64K buffer at once and trying to > free it page by page. > > I need some help to resolve this issue. > > Performance wise there is a huge jump in throughput. Are you sure? The bandwith issue should be on the usb device side, not the network from what I have seen. What type of device are you testing this with? thanks, greg k-h