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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC5D4C33CA9 for ; Mon, 13 Jan 2020 16:02:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A0FA2206DA for ; Mon, 13 Jan 2020 16:02:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728850AbgAMQCP (ORCPT ); Mon, 13 Jan 2020 11:02:15 -0500 Received: from mail-pj1-f66.google.com ([209.85.216.66]:40005 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728650AbgAMQCP (ORCPT ); Mon, 13 Jan 2020 11:02:15 -0500 Received: by mail-pj1-f66.google.com with SMTP id bg7so4452519pjb.5 for ; Mon, 13 Jan 2020 08:02:14 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=jPhzziPcXw+kQ4qYAw+8rAi/yrPBcu23BsMPHcjLs80=; b=C0Y/LHSSe2TU+4uu9q0rnjwO6ObCBrntnRlBbaSJd7Yr9HoDu5eIwdmXkkOG3ciJCU hxLmK+BIiY1WpunxZ7Dqea8iNZlpR6+Wb4pErefbIIJitMvRiFozTYyTKfjUaQCzW/Xs al9VGqCuXz3JWyGuzzbzjn7lMZn46i+CtiRwAyQXWsFti9PDenzHEnHeRMXqyR0eWGHP dsG1zQAjRPijNyEH1HbhN92PaccVXqDnNEVGyRzuF6s/3TgHU23lLZoHVer3s3/qT8LA krTJDc7bPk5MUp8LHIBqJdFgf2mHsCxCvu3/zCsWAZYibax6FzAq+t2i8oM3TPXGnU+r SR3w== X-Gm-Message-State: APjAAAWjj8KHASgjZm16Pc+r5esN5S/nbafdRxu6nfldQygNLKAx4qhS UGP5nkxdEWR3CsszsmEMrQRpRtnU X-Google-Smtp-Source: APXvYqwSkzgTJ3WWc0cSZTc2gfV/cjMZCsY8kvE0jk+bx/pXUcI/idcTd2EFZhl/tpEvWw9i8KurXQ== X-Received: by 2002:a17:902:7602:: with SMTP id k2mr20931413pll.34.1578931333180; Mon, 13 Jan 2020 08:02:13 -0800 (PST) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id 65sm15063826pfu.140.2020.01.13.08.02.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Jan 2020 08:02:12 -0800 (PST) Subject: Re: [PATCH v2 1/6] locking/lockdep: Track number of zapped classes To: Waiman Long , Peter Zijlstra Cc: Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org References: <20191216151517.7060-1-longman@redhat.com> <20191216151517.7060-2-longman@redhat.com> <20200113145542.GV2844@hirez.programming.kicks-ass.net> <137a3e75-ca3c-2222-d2af-a6b7bb692b66@redhat.com> From: Bart Van Assche Message-ID: <2e9d25b1-f61a-2367-36f3-7b39a9cca095@acm.org> Date: Mon, 13 Jan 2020 08:02:11 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <137a3e75-ca3c-2222-d2af-a6b7bb692b66@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/13/20 6:58 AM, Waiman Long wrote: > On 1/13/20 9:55 AM, Peter Zijlstra wrote: >> On Mon, Dec 16, 2019 at 10:15:12AM -0500, Waiman Long wrote: >>> The whole point of the lockdep dynamic key patch is to allow unused >>> locks to be removed from the lockdep data buffers so that existing >>> buffer space can be reused. However, there is no way to find out how >>> many unused locks are zapped and so we don't know if the zapping process >>> is working properly. >>> >>> Add a new nr_zapped_classes variable to track that and show it in >>> /proc/lockdep_stats if it is non-zero. >>> >>> diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c >>> index dadb7b7fba37..d98d349bb648 100644 >>> --- a/kernel/locking/lockdep_proc.c >>> +++ b/kernel/locking/lockdep_proc.c >>> @@ -336,6 +336,15 @@ static int lockdep_stats_show(struct seq_file *m, void *v) >>> seq_printf(m, " debug_locks: %11u\n", >>> debug_locks); >>> >>> + /* >>> + * Zappped classes and lockdep data buffers reuse statistics. >>> + */ >>> + if (!nr_zapped_classes) >>> + return 0; >>> + >>> + seq_puts(m, "\n"); >>> + seq_printf(m, " zapped classes: %11lu\n", >>> + nr_zapped_classes); >>> return 0; >>> } >> Why is that conditional? >> > Because I thought zapping class doesn't occur that often. Apparently, > class zapping happens when the system first boots up. I guess that > conditional check isn't needed. I can remove it in the next version. Zapping a lock class happens every time a lock key is unregistered. That can happen any time as one can see in the following grep output: $ git grep -lw 'lockdep_unregister_key' drivers/net/bonding/bond_main.c:4446: lockdep_unregister_key(&bond->stats_lock_key); drivers/net/team/team.c:1676: lockdep_unregister_key(&team->team_lock_key); drivers/net/team/team.c:1984: lockdep_unregister_key(&team->team_lock_key); include/linux/lockdep.h:294:extern void lockdep_unregister_key(struct lock_class_key *key); include/linux/lockdep.h:464:static inline void lockdep_unregister_key(struct lock_class_key *key) kernel/locking/lockdep.c:5166:void lockdep_unregister_key(struct lock_class_key *key) kernel/locking/lockdep.c:5201:EXPORT_SYMBOL_GPL(lockdep_unregister_key); kernel/workqueue.c:3456: lockdep_unregister_key(&wq->key); net/core/dev.c:9172: lockdep_unregister_key(&dev->qdisc_tx_busylock_key); net/core/dev.c:9173: lockdep_unregister_key(&dev->qdisc_running_key); net/core/dev.c:9174: lockdep_unregister_key(&dev->qdisc_xmit_lock_key); net/core/dev.c:9175: lockdep_unregister_key(&dev->addr_list_lock_key); net/core/dev.c:9183: lockdep_unregister_key(&dev->qdisc_xmit_lock_key); net/core/dev.c:9184: lockdep_unregister_key(&dev->addr_list_lock_key); tools/lib/lockdep/include/liblockdep/common.h:48:void lockdep_unregister_key(struct lock_class_key *key); tools/lib/lockdep/include/liblockdep/mutex.h:58: lockdep_unregister_key(&lock->key); Bart.