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[23.128.96.18]) by mx.google.com with ESMTP id ks17si849343ejb.366.2020.05.26.17.32.41; Tue, 26 May 2020 17:33:03 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=glasLEIM; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391287AbgEZUbW (ORCPT + 99 others); Tue, 26 May 2020 16:31:22 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:51572 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389096AbgEZUbV (ORCPT ); Tue, 26 May 2020 16:31:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590525080; 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=c5HsvkOS39/pqJszGcOndT9nAZ5CE8YwcSNpRDQR19E=; b=glasLEIMaePFeMSDMGMlSshMNVS/Vg6BOOtWY23mCGZVb7ObQKKSjKJg+UuMgtSfrjKwKH 3IjZdB0XqneagGYnn2RyifRlGcXB80M2c9UPT+e6fccupath44525ult7flfg73l+zGfH9 hy8ejbNE+BciowxEHxXFm4gDjPRN3d8= 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-302-m1fjb71ROuu8T7Pn8UUmZQ-1; Tue, 26 May 2020 16:31:00 -0400 X-MC-Unique: m1fjb71ROuu8T7Pn8UUmZQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DD22A107ACCA; Tue, 26 May 2020 20:30:59 +0000 (UTC) Received: from llong.remote.csb (ovpn-115-53.rdu2.redhat.com [10.10.115.53]) by smtp.corp.redhat.com (Postfix) with ESMTP id 15C975C1C5; Tue, 26 May 2020 20:30:58 +0000 (UTC) Subject: Re: [PATCH] locking/lockdep: Increase MAX_LOCKDEP_ENTRIES by half To: Peter Zijlstra , Qian Cai Cc: Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org References: <20200526174349.8312-1-longman@redhat.com> <20200526185850.GE991@lca.pw> <20200526195630.GF325280@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: Date: Tue, 26 May 2020 16:30:58 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200526195630.GF325280@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/26/20 3:56 PM, Peter Zijlstra wrote: > On Tue, May 26, 2020 at 02:58:50PM -0400, Qian Cai wrote: > >> I still don't understand why reading all sysfs files on this system >> could increase that much, but here is the lockdep file after >> running sysfs read to see if you could spot anything obviously, >> >> https://cailca.github.io/files/lockdep.txt > 00000000f011a2a5 OPS: 20 FD: 45 BD: 1 .+.+: kn->active#834 > > is that somewhere near the number of CPUs you have? > > Anyway, there's very long "kn->active#..." chains in there, which seems > to suggest some annotation is all sorts of buggered. > It is actually one active lock per instance of the kerfs_node structures. That means more than 800 sysfs files are accessed in some way. As we could have much more than 800 sysfs files in the system, we could easily overwhelm the lockdep tables if we really try to access all of them. Cheers, Longman