From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 22 Sep 2002 17:24:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 22 Sep 2002 17:24:23 -0400 Received: from igw3.watson.ibm.com ([198.81.209.18]:24533 "EHLO igw3.watson.ibm.com") by vger.kernel.org with ESMTP id ; Sun, 22 Sep 2002 17:24:23 -0400 From: bob MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Date: Sun, 22 Sep 2002 17:29:21 -0400 (EDT) To: Linus Torvalds Cc: Roman Zippel , okrieg@us.ibm.com, trz@us.ibm.com, Ingo Molnar , Karim Yaghmour , linux-kernel , LTT-Dev Subject: Re: [ltt-dev] Re: [PATCH] LTT for 2.5.38 1/9: Core infrastructure In-Reply-To: References: X-Mailer: VM 6.43 under 20.4 "Emerald" XEmacs Lucid Message-ID: <15758.13368.993118.889319@k42.watson.ibm.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Linus Torvalds writes: > > >From what I've seen from the LTT thing, it's too heavy-weight to be good Not true anymore. > I suspect we'll want to have some form of event tracing eventually, but > I'm personally pretty convinced that it needs to be a per-CPU thing, and > the core mechanism would need to be very lightweight. It's easier to build > up complexity on top of a lightweight interface than it is to make a > lightweight interface out of a heavy one. We have removed locks (code now atomically reserves space in the trace buffer), significantly reduced the cost of taking timestamps by using the real-time clock, and are in the process of implementing per-CPU buffers. As per previous email, the intent is to get only the core infrastructure into the kernel and keep trace points as patches. Some of the work going into LTT is modeled after the tracing infrastructure in K42, which is extremely lightweight, lock-free, and designed for multiprocessors. Robert Wisniewski The K42 MP OS Project Advanced Operating Systems Scalable Parallel Systems IBM T.J. Watson Research Center 914-945-3181 http://www.research.ibm.com/K42/ bob@watson.ibm.com