From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 998876B0268 for ; Thu, 19 Oct 2017 01:57:34 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id n4so3440599wrb.8 for ; Wed, 18 Oct 2017 22:57:34 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id b5sor5852930wrf.66.2017.10.18.22.57.33 for (Google Transport Security); Wed, 18 Oct 2017 22:57:33 -0700 (PDT) Date: Thu, 19 Oct 2017 07:57:30 +0200 From: Ingo Molnar Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default Message-ID: <20171019055730.mlpoz333ekflacs2@gmail.com> References: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> <20171018100944.g2mc6yorhtm5piom@gmail.com> <20171019043240.GA3310@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171019043240.GA3310@X58A-UD3R> Sender: owner-linux-mm@kvack.org List-ID: To: Byungchul Park Cc: peterz@infradead.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@lge.com, Linus Torvalds * 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? 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 and false positives are fixed by the next merge window. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org