From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754133AbYKFONi (ORCPT ); Thu, 6 Nov 2008 09:13:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750932AbYKFONa (ORCPT ); Thu, 6 Nov 2008 09:13:30 -0500 Received: from casper.infradead.org ([85.118.1.10]:55091 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751025AbYKFON3 (ORCPT ); Thu, 6 Nov 2008 09:13:29 -0500 Date: Thu, 6 Nov 2008 06:14:08 -0800 From: Arjan van de Ven To: Peter Zijlstra Cc: Steven Rostedt , linux-kernel@vger.kernel.org, mingo@elte.hu Subject: Re: [PATCH] ftrace: add an fsync tracer Message-ID: <20081106061408.03c10337@infradead.org> In-Reply-To: <1225976138.7803.4485.camel@twins> References: <20081105094902.27ec4b39@infradead.org> <1225976138.7803.4485.camel@twins> Organization: Intel X-Mailer: Claws Mail 3.6.0 (GTK+ 2.14.4; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 06 Nov 2008 13:55:38 +0100 Peter Zijlstra wrote: > On Wed, 2008-11-05 at 09:49 -0800, Arjan van de Ven wrote: > > From 63c1b869d94eb31a98015af09fb24e22151f2f00 Mon Sep 17 00:00:00 > > 2001 From: Arjan van de Ven > > Date: Tue, 4 Nov 2008 21:08:11 -0800 > > Subject: [PATCH] ftrace: add an fsync tracer > > > > fsync() (and its cousin, fdatasync()) are important chokepoints in > > the kernel as they imply very expensive operations, both in terms > > of filesystem operations (ext3 writes back its entire journal) as > > well as the block layer (fsync() implies sending a cache flushing > > barrier to the SATA/SCSI disk). > > > > This tracer makes a log of which application calls fsync() on which > > file, so that developers and others interested in finding these > > choke points can locate them and fix them in the apps that call > > this function. > > Sorry, but I have to object to such single purpose tracers.. > > If we go this way we'll end up with a gazillion little tracers, non of > which are really useful. > > Please work on getting something like a syscall tracer, or lttng like > event tracer. > btw a syscall tracer is not long term right, just like system call level auditing was the wrong thing: you don't have the real information of what's being worked on. having the trace points on the do_FOO() level is the right thing, and that's exactly what my patch does.