From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 6FD6B6B0038 for ; Thu, 24 Nov 2016 12:32:37 -0500 (EST) Received: by mail-wm0-f70.google.com with SMTP id w13so16418537wmw.0 for ; Thu, 24 Nov 2016 09:32:37 -0800 (PST) Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk. [195.92.253.2]) by mx.google.com with ESMTPS id p123si9313816wmg.154.2016.11.24.09.32.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 24 Nov 2016 09:32:35 -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-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: 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 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