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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 772F7C33CAD for ; Mon, 13 Jan 2020 14:58:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 498E32081E for ; Mon, 13 Jan 2020 14:58:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NHEwTrMw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729019AbgAMO6k (ORCPT ); Mon, 13 Jan 2020 09:58:40 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:21796 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728843AbgAMO6j (ORCPT ); Mon, 13 Jan 2020 09:58:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578927518; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0iWBtjb/6H1xhRa1v3TPsGTDIS/S6k7aw42PEobHbYw=; b=NHEwTrMwfykcAI9PlOKEyLWzwEk2kqwhdHXX0lnKwmpJXJEceD3txx5Ukso34rn0fIUR+r 8H02ydPX/eKZ/NS3W4jWmhR/gsW6BU/I4sQ8/zBWIyzfaYVvoqAWA8V6DVKfmgZYsWuufQ eHr0eKVeeYBOX3z+eEbEx1q6mXKH6cs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-195-a5a4ngezNMODdqjQUq1ofA-1; Mon, 13 Jan 2020 09:58:31 -0500 X-MC-Unique: a5a4ngezNMODdqjQUq1ofA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 522D31856A63; Mon, 13 Jan 2020 14:58:30 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-59.bos.redhat.com [10.18.17.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id B3F3560BE2; Mon, 13 Jan 2020 14:58:29 +0000 (UTC) Subject: Re: [PATCH v2 1/6] locking/lockdep: Track number of zapped classes To: Peter Zijlstra Cc: Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org, Bart Van Assche References: <20191216151517.7060-1-longman@redhat.com> <20191216151517.7060-2-longman@redhat.com> <20200113145542.GV2844@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: <137a3e75-ca3c-2222-d2af-a6b7bb692b66@redhat.com> Date: Mon, 13 Jan 2020 09:58:29 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200113145542.GV2844@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Cheers, Longman