From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD375C433EF for ; Wed, 9 Feb 2022 09:10:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235087AbiBIJKQ (ORCPT ); Wed, 9 Feb 2022 04:10:16 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:49264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233465AbiBIJKA (ORCPT ); Wed, 9 Feb 2022 04:10:00 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA8C7E078229; Wed, 9 Feb 2022 01:09:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kNBxEECZ8nYVRQBlRi4s4bPsYk+6wGvc+UHQLe+LfQY=; b=FuT01ILcnQE1hlwV0N6QoRzje7 8leIgTUsGHbhfy7cNPjN8ZrjHcSG0wypOKtgyb8t04GcdHB5bH2yXofjaCs8wpl1CIqqOkec3R9OV nApYAVlzrV8ZfypyHa4mIELkzUQhBcEibVe6rjqueMf/NegoUT6rvZNNsoc4Uw2YqsFP9t1UTNqIf jNC72U1XwX8JGYxfA0nQlHqSjCcVfzkGjPBeAtSDlLt6otVC5r0jjKiMiAMeC9xmjVZ1sMuKSSBys rCFVdCTkXxb8dN7UTtpmiYJWVdWQaduq6Qanmd7JpqkCzBgIpJKnbvw5fQS2u7k6VjPF4p+ScGV/Y cDMFRHqA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nHiyL-007ELN-4I; Wed, 09 Feb 2022 09:09:09 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id B7873986226; Wed, 9 Feb 2022 10:09:08 +0100 (CET) Date: Wed, 9 Feb 2022 10:09:08 +0100 From: Peter Zijlstra To: Namhyung Kim Cc: Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , LKML , Thomas Gleixner , Steven Rostedt , Byungchul Park , "Paul E. McKenney" , Mathieu Desnoyers , Radoslaw Burny , Tejun Heo , rcu@vger.kernel.org, cgroups@vger.kernel.org, linux-btrfs@vger.kernel.org, intel-gfx@lists.freedesktop.org Subject: Re: [RFC 00/12] locking: Separate lock tracepoints from lockdep/lock_stat (v1) Message-ID: <20220209090908.GK23216@worktop.programming.kicks-ass.net> References: <20220208184208.79303-1-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220208184208.79303-1-namhyung@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 08, 2022 at 10:41:56AM -0800, Namhyung Kim wrote: > Eventually I'm mostly interested in the contended locks only and I > want to reduce the overhead in the fast path. By moving that, it'd be > easy to track contended locks with timing by using two tracepoints. So why not put in two new tracepoints and call it a day? Why muck about with all that lockdep stuff just to preserve the name (and in the process continue to blow up data structures etc..). This leaves distros in a bind, will they enable this config and provide tracepoints while bloating the data structures and destroying things like lockref (which relies on sizeof(spinlock_t)), or not provide this at all. Yes, the name is convenient, but it's just not worth it IMO. It makes the whole proposition too much of a trade-off. Would it not be possible to reconstruct enough useful information from the lock callsite?