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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 A85EEC433DF for ; Tue, 26 May 2020 17:44:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8226320704 for ; Tue, 26 May 2020 17:44:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="b0s4eSwR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728810AbgEZRoY (ORCPT ); Tue, 26 May 2020 13:44:24 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:34194 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726930AbgEZRoY (ORCPT ); Tue, 26 May 2020 13:44:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590515061; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=ikyw/aUF3Qy2tXbuYHy4ZgKqsS/cw/f1Zn/iqfDGVeU=; b=b0s4eSwRc3TmNmSOyq84laT6qWLbzPZWEFUk/lN/CWeoj7GCN9ufSajuOdm1omDtN86IpQ YKzlQ7dbanvhnjtgjyxs79ga1dvHabK2bolt8/nJsVptmOD9p9Mpdx6P/DEkmX5XAHrVlr ClAQJ9XOxOyb0qBxxJ02kTgsqGGYf2o= 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-333-Ca5Zx3YaMUmWyedi8SHmLg-1; Tue, 26 May 2020 13:44:17 -0400 X-MC-Unique: Ca5Zx3YaMUmWyedi8SHmLg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1FB31100CCCA; Tue, 26 May 2020 17:44:16 +0000 (UTC) Received: from llong.com (ovpn-115-53.rdu2.redhat.com [10.10.115.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id AAE7919D61; Tue, 26 May 2020 17:44:10 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon Cc: linux-kernel@vger.kernel.org, Qian Cai , Waiman Long Subject: [PATCH] locking/lockdep: Increase MAX_LOCKDEP_ENTRIES by half Date: Tue, 26 May 2020 13:43:49 -0400 Message-Id: <20200526174349.8312-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It was found by Qian Cai that lockdep splat sometimes appears with the "BUG: MAX_LOCKDEP_ENTRIES too low" message on linux-next. On a 32-vcpu VM guest with a v5.7-rc7 based kernel, I looked at how many of the various table entries were being used after bootup and after a parallel kernel build (make -j32). The tables below show the usage statistics. After bootup: Table Used Max %age ----- ---- --- ---- lock_classes[] 1834 8192 22.4 list_entries[] 15646 32768 47.7 lock_chains[] 20873 65536 31.8 chain_hlocks[] 83199 327680 25.4 stack_trace[] 146177 524288 27.9 After parallel kernel build: Table Used Max %age ----- ---- --- ---- lock_classes[] 1864 8192 22.8 list_entries[] 17134 32768 52.3 lock_chains[] 25196 65536 38.4 chain_hlocks[] 106321 327680 32.4 stack_trace[] 158700 524288 30.3 Percentage-wise, it can be seen that the list_entries for direct dependencies are used much more than the other tables. So it is also the table that is mostly likely to run out of space when running a compex workload. To reduce the likelihood of running out of table entries, we can increase MAX_LOCKDEP_ENTRIES by 50% from 16384/32768 to 24576/49152. On a 64-bit architecture, that represents an increase in memory consumption of 917504 bytes. With that change, the percentage usage of list_entries[] will fall to 31.8% and 34.9% respectively to make them more in line with the other tables. Signed-off-by: Waiman Long --- kernel/locking/lockdep_internals.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h index baca699b94e9..6108d2fbe775 100644 --- a/kernel/locking/lockdep_internals.h +++ b/kernel/locking/lockdep_internals.h @@ -89,12 +89,12 @@ static const unsigned long LOCKF_USED_IN_IRQ_READ = * table (if it's not there yet), and we check it for lock order * conflicts and deadlocks. */ -#define MAX_LOCKDEP_ENTRIES 16384UL +#define MAX_LOCKDEP_ENTRIES 24576UL #define MAX_LOCKDEP_CHAINS_BITS 15 #define MAX_STACK_TRACE_ENTRIES 262144UL #define STACK_TRACE_HASH_SIZE 8192 #else -#define MAX_LOCKDEP_ENTRIES 32768UL +#define MAX_LOCKDEP_ENTRIES 49152UL #define MAX_LOCKDEP_CHAINS_BITS 16 -- 2.18.1