From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753526AbbAJArz (ORCPT ); Fri, 9 Jan 2015 19:47:55 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:39040 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751381AbbAJArx (ORCPT ); Fri, 9 Jan 2015 19:47:53 -0500 Date: Fri, 9 Jan 2015 16:47:52 -0800 From: Greg Kroah-Hartman To: Sudeep Dutt Cc: Arnd Bergmann , Jonathan Corbet , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Dave Jiang , Nikhil Rao , Ashutosh Dixit Subject: Re: [PATCH char-misc-next 02/13] misc: mic: SCIF ring buffer infrastructure Message-ID: <20150110004752.GA4171@kroah.com> References: <6a99cdd6459ca70802f0000c1904bfdb8f45b73b.1418237176.git.sudeep.dutt@intel.com> <20150109230526.GB3614@kroah.com> <1420849699.6393.33.camel@rbtaylor-desk1.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1420849699.6393.33.camel@rbtaylor-desk1.amr.corp.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 09, 2015 at 04:28:19PM -0800, Sudeep Dutt wrote: > On Fri, 2015-01-09 at 15:05 -0800, Greg Kroah-Hartman wrote: > > On Wed, Dec 10, 2014 at 11:47:42AM -0800, Sudeep Dutt wrote: > > > SCIF ring buffer is a single producer, single consumer byte stream ring > > > buffer optimized for avoiding reads across the PCIe bus. The ring buffer is > > > used to implement a receive queue for SCIF driver messaging between nodes and > > > for byte stream messaging between SCIF endpoints. Each SCIF node has a > > > receive queue for every other SCIF node, and each connected endpoint has a > > > receive queue for messages from its peer. This pair of receive queues is > > > referred to as a SCIF queue pair. > > > > And the reason you aren't using the built-in kernel ring buffer code is > > why? > > > > This simple byte stream ring buffer is in our performance data path for > small messages and is optimized to avoid reads across the PCIe bus while > adding the required barriers and hardware workarounds for the MIC > Coprocessor. I will add some more documentation here in the v2 which I > will post early next week. > > We did not find other ring buffers in the kernel which were tailored for > our use case across PCIe. I am guessing (please correct me) that you are > referring to the ring buffer in include/linux/ring_buffer.h. It does not > seem to be designed for being used between two independent OS's across > the PCIe bus. Please let me know your thoughts. No, it's designed for an in-kernel ringbuffer, so you need to document exactly this. thanks, greg k-h