Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934093Ab2FENQk (ORCPT ); Tue, 5 Jun 2012 09:16:40 -0400 Received: from s15943758.onlinehome-server.info ([217.160.130.188]:36122 "EHLO mail.x86-64.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760103Ab2FENKG (ORCPT ); Tue, 5 Jun 2012 09:10:06 -0400 Date: Tue, 5 Jun 2012 15:10:31 +0200 From: Borislav Petkov To: Yoshihiro YUNOMAE Cc: linux-kernel@vger.kernel.org, Cam Macdonell , Arnaldo Carvalho de Melo , Borislav Petkov , Grant Likely , Greg Kroah-Hartman , Joerg Roedel , Linus Walleij , MyungJoo Ham , Ohad Ben-Cohen , Rusty Russell , qemu-devel@nongnu.org, systemtap@sourceware.org, yrl.pp-manager.tt@hitachi.com, Masami Hiramatsu , Akihiro Nagai Subject: Re: [RFC PATCH 1/2] ivring: Add a ring-buffer driver on IVShmem Message-ID: <20120605131031.GF13495@aftab.osrc.amd.com> References: <20120605104954.15442.62695.stgit@ltc189.sdl.hitachi.co.jp> <20120605130117.15479.32680.stgit@ltc189.sdl.hitachi.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120605130117.15479.32680.stgit@ltc189.sdl.hitachi.co.jp> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1911 Lines: 42 On Tue, Jun 05, 2012 at 10:01:17PM +0900, Yoshihiro YUNOMAE wrote: > This patch adds a ring-buffer driver for IVShmem device, a virtual RAM device in > QEMU. This driver can be used as a ring-buffer for kernel logging or tracing of > a guest OS by recording kernel programing or SystemTap. > > This ring-buffer driver is implemented very simple. First 4kB of shared memory > region is control structure of a ring-buffer. In this region, some values for > managing the ring-buffer is stored such as bits and mask of whole memory size, > writing position, threshold value for notification to a reader on a host OS. > This region is used by the reader to know writing position. Then, "total > memory size - 4kB" equals to usable memory region for recording data. > This ring-buffer driver records any data from start to end of the writable > memory region. > > When writing size exceeds a threshold value, this driver can notify a reader > to read data by using writel(). As this later patch, reader does not have any > function for receiving the notification. This notification feature will be used > near the future. > > As a writer records data in this ring-buffer, spinlock function is used to > avoid competing by some writers in multi CPU environment. Not to use spinlock, > lockless ring-buffer like as ftrace and one ring-buffer one CPU will be > implemented near the future. Yet another ring buffer? We already have an ftrace and perf ring buffer, can't you use one of those? -- Regards/Gruss, Boris. Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/