From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [195.92.253.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 8330B81E5D for ; Thu, 24 Nov 2016 09:32:37 -0800 (PST) Date: Thu, 24 Nov 2016 17:32:20 +0000 From: Al Viro Subject: Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing Message-ID: <20161124173220.GR1555@ZenIV.linux.org.uk> References: <1479926662-21718-1-git-send-email-ross.zwisler@linux.intel.com> <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Ross Zwisler Cc: Jan Kara , Matthew Wilcox , linux-nvdimm@lists.01.org, Dave Chinner , linux-kernel@vger.kernel.org, Steven Rostedt , Christoph Hellwig , linux-mm@kvack.org, Ingo Molnar , linux-fsdevel@vger.kernel.org, Andrew Morton , linux-ext4@vger.kernel.org List-ID: On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the PMD fault handler. This allows the tracing for DAX to > be done in the same way as the filesystem tracing so that developers can > look at them together and get a coherent idea of what the system is doing. It also has one hell of potential for becoming a massive nuisance. Keep in mind that if any userland code becomes dependent on those - that's it, they have become parts of stable userland ABI and are to be maintained indefinitely. Don't expect "tracepoints are special case" to prevent that. So treat anything you add in that manner as potential stable ABI you might have to keep around forever. It's *not* a glorified debugging printk. _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934780AbcKXRc3 (ORCPT ); Thu, 24 Nov 2016 12:32:29 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:42654 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933887AbcKXRc2 (ORCPT ); Thu, 24 Nov 2016 12:32:28 -0500 Date: Thu, 24 Nov 2016 17:32:20 +0000 From: Al Viro To: Ross Zwisler Cc: linux-kernel@vger.kernel.org, Andrew Morton , Christoph Hellwig , Dan Williams , Dave Chinner , Ingo Molnar , Jan Kara , Matthew Wilcox , Steven Rostedt , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@ml01.01.org Subject: Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing Message-ID: <20161124173220.GR1555@ZenIV.linux.org.uk> References: <1479926662-21718-1-git-send-email-ross.zwisler@linux.intel.com> <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the PMD fault handler. This allows the tracing for DAX to > be done in the same way as the filesystem tracing so that developers can > look at them together and get a coherent idea of what the system is doing. It also has one hell of potential for becoming a massive nuisance. Keep in mind that if any userland code becomes dependent on those - that's it, they have become parts of stable userland ABI and are to be maintained indefinitely. Don't expect "tracepoints are special case" to prevent that. So treat anything you add in that manner as potential stable ABI you might have to keep around forever. It's *not* a glorified debugging printk. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 24 Nov 2016 17:32:20 +0000 From: Al Viro To: Ross Zwisler Cc: linux-kernel@vger.kernel.org, Andrew Morton , Christoph Hellwig , Dan Williams , Dave Chinner , Ingo Molnar , Jan Kara , Matthew Wilcox , Steven Rostedt , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org Subject: Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing Message-ID: <20161124173220.GR1555@ZenIV.linux.org.uk> References: <1479926662-21718-1-git-send-email-ross.zwisler@linux.intel.com> <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the PMD fault handler. This allows the tracing for DAX to > be done in the same way as the filesystem tracing so that developers can > look at them together and get a coherent idea of what the system is doing. It also has one hell of potential for becoming a massive nuisance. Keep in mind that if any userland code becomes dependent on those - that's it, they have become parts of stable userland ABI and are to be maintained indefinitely. Don't expect "tracepoints are special case" to prevent that. So treat anything you add in that manner as potential stable ABI you might have to keep around forever. It's *not* a glorified debugging printk. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH 3/6] dax: add tracepoint infrastructure, PMD tracing Date: Thu, 24 Nov 2016 17:32:20 +0000 Message-ID: <20161124173220.GR1555@ZenIV.linux.org.uk> References: <1479926662-21718-1-git-send-email-ross.zwisler@linux.intel.com> <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, Andrew Morton , Christoph Hellwig , Dan Williams , Dave Chinner , Ingo Molnar , Jan Kara , Matthew Wilcox , Steven Rostedt , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org To: Ross Zwisler Return-path: Content-Disposition: inline In-Reply-To: <1479926662-21718-4-git-send-email-ross.zwisler@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed, Nov 23, 2016 at 11:44:19AM -0700, Ross Zwisler wrote: > Tracepoints are the standard way to capture debugging and tracing > information in many parts of the kernel, including the XFS and ext4 > filesystems. Create a tracepoint header for FS DAX and add the first DAX > tracepoints to the PMD fault handler. This allows the tracing for DAX to > be done in the same way as the filesystem tracing so that developers can > look at them together and get a coherent idea of what the system is doing. It also has one hell of potential for becoming a massive nuisance. Keep in mind that if any userland code becomes dependent on those - that's it, they have become parts of stable userland ABI and are to be maintained indefinitely. Don't expect "tracepoints are special case" to prevent that. So treat anything you add in that manner as potential stable ABI you might have to keep around forever. It's *not* a glorified debugging printk.