From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754522AbcGHKIc (ORCPT ); Fri, 8 Jul 2016 06:08:32 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36252 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753018AbcGHKIY (ORCPT ); Fri, 8 Jul 2016 06:08:24 -0400 Date: Fri, 8 Jul 2016 12:08:19 +0200 From: Ingo Molnar To: Byungchul Park Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, walken@google.com, =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Josh Poimboeuf , Peter Zijlstra Subject: Re: [PATCH 1/2] x86/dumpstack: Optimize save_stack_trace Message-ID: <20160708100819.GA17300@gmail.com> References: <1467628075-7289-1-git-send-email-byungchul.park@lge.com> <20160707101740.GF2279@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160707101740.GF2279@X58A-UD3R> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Byungchul Park wrote: > On Mon, Jul 04, 2016 at 07:27:54PM +0900, Byungchul Park wrote: > > I suggested this patch on https://lkml.org/lkml/2016/6/20/22. However, > > I want to proceed saperately since it's somewhat independent from each > > other. Frankly speaking, I want this patchset to be accepted at first so > > that the crossfeature can use this optimized save_stack_trace_norm() > > which makes crossrelease work smoothly. > > What do you think about this way to improve it? I like both of your improvements, the speed up is impressive: [ 2.327597] save_stack_trace() takes 87114 ns ... [ 2.781694] save_stack_trace() takes 20044 ns ... [ 3.103264] save_stack_trace takes 3821 (sched_lock) Could you please also measure call graph recording (perf record -g), how much faster does it get with your patches and what are our remaining performance hot spots? Could you please merge your patches to the latest -tip tree, because this commit I merged earlier today: 81c2949f7fdc x86/dumpstack: Add show_stack_regs() and use it conflicts with your patches. (I'll push this commit out later today.) Also, could you please rename the _norm names to _fast or so, to signal that this is a faster but less reliable method to get a stack dump? Nobody knows what '_norm' means, but '_fast' is pretty self-explanatory. Thanks, Ingo