Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756584Ab1DFSu6 (ORCPT ); Wed, 6 Apr 2011 14:50:58 -0400 Received: from smtp-out.google.com ([74.125.121.67]:22050 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756518Ab1DFSu5 (ORCPT ); Wed, 6 Apr 2011 14:50:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:from:date:message-id:subject:to:cc:content-type; b=Ov9VtEnLf9I1P/NQdcEtjTXS6W7sN7ML0PS1hklofv10IUVZKWrc84XsMCMk1JkbU9 O7CKEM83VmWlFE/ezfxw== MIME-Version: 1.0 From: Vaibhav Nagarnaik Date: Wed, 6 Apr 2011 11:50:21 -0700 Message-ID: Subject: [RFC] tracing: Adding cgroup aware tracing functionality To: Paul Menage , Li Zefan , Stephane Eranian , Andrew Morton , Steven Rostedt , Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2071 Lines: 46 All The cgroup functionality is being used widely in different scenarios. It also is being integrated with other parts of kernel to take advantage of its features. One of the areas that is not yet aware of cgroup functionality is the ftrace framework. Although ftrace provides a way to filter based on PIDs of tasks to be traced, it is restricted to specific tracers, like function tracer. Also it becomes difficult to keep track of all PIDs in a dynamic environment with processes being created and destroyed in a short amount of time. An application that creates many processes/tasks is convenient to track and control with cgroups, but it is difficult to track these processes for the purposes of tracing. And if child processes are moved to another cgroup, it makes sense to trace only the original cgroup. This proposal is to create a file in the tracing directory called set_trace_cgroup to which a user can write the path of an active cgroup, one at a time. If no cgroups are specified, no filtering is done and all tasks are traced. When a cgroup path is added in, it sets a boolean tracing_enabled for the enabled cgroup in all the hierarchies, which enables tracing for all the assigned tasks under the specified cgroup. Though creating a new file in the directory is not desirable, but this interface seems the most appropriate change required to implement the new feature. This tracing_enabled flag is also exported in the cgroupfs directory structure which can be turned on/off for a specific hierarchy/cgroup combination. This gives control to enable/disable tracing over a cgroup in a specific hierarchy only. This gives more fine-grained control over the tasks being traced. I would like to know your thoughts on this interface and the approach to make tracing cgroup aware. Thanks Vaibhav Nagarnaik -- 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/