From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751417AbdJSGLR (ORCPT ); Thu, 19 Oct 2017 02:11:17 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:55061 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751014AbdJSGLP (ORCPT ); Thu, 19 Oct 2017 02:11:15 -0400 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Thu, 19 Oct 2017 15:11:12 +0900 From: Byungchul Park To: Ingo Molnar Cc: peterz@infradead.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@lge.com, Linus Torvalds Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default Message-ID: <20171019061112.GB3310@X58A-UD3R> References: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> <20171018100944.g2mc6yorhtm5piom@gmail.com> <20171019043240.GA3310@X58A-UD3R> <20171019055730.mlpoz333ekflacs2@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171019055730.mlpoz333ekflacs2@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 19, 2017 at 07:57:30AM +0200, Ingo Molnar wrote: > > * Byungchul Park wrote: > > > On Wed, Oct 18, 2017 at 12:09:44PM +0200, Ingo Molnar wrote: > > > BTW., have you attempted limiting the depth of the stack traces? I suspect more > > > than 2-4 are rarely required to disambiguate the calling context. > > > > I did it for you. Let me show you the result. > > > > 1. No lockdep: 2.756558155 seconds time elapsed ( +- 0.09% ) > > 2. Lockdep: 2.968710420 seconds time elapsed ( +- 0.12% ) > > 3. Lockdep + Crossrelease 5 entries: 3.153839636 seconds time elapsed ( +- 0.31% ) > > 4. Lockdep + Crossrelease 3 entries: 3.137205534 seconds time elapsed ( +- 0.87% ) > > 5. Lockdep + Crossrelease + This patch: 2.963669551 seconds time elapsed ( +- 0.11% ) > > I think the lockdep + crossrelease + full-stack numbers are missing? Ah, the last version of crossrelease merged into vanilla, records 5 entries, since I thought it overloads too much if full stack is used, and 5 entries are enough. Don't you think so? > But yeah, looks like single-entry-stacktrace crossrelease only has a +0.2% > performance cost (with 0.1% noise), while lockdep itself has a +7.7% cost. > > That's very reasonable and we can keep the single-entry cross-release feature > enabled by default as part of CONFIG_PROVE_LOCKING=y - assuming all the crashes BTW, is there any crash by cross-release I don't know? Of course, I know cases of false positives, but I don't about crash. Thanks, Byungchul > and false positives are fixed by the next merge window. > > Thanks, > > Ingo