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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 E1815C742D2 for ; Fri, 12 Jul 2019 23:03:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6583204FD for ; Fri, 12 Jul 2019 23:03:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728108AbfGLXDX (ORCPT ); Fri, 12 Jul 2019 19:03:23 -0400 Received: from mail-pl1-f169.google.com ([209.85.214.169]:39772 "EHLO mail-pl1-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727698AbfGLXDW (ORCPT ); Fri, 12 Jul 2019 19:03:22 -0400 Received: by mail-pl1-f169.google.com with SMTP id b7so5462458pls.6 for ; Fri, 12 Jul 2019 16:03:22 -0700 (PDT) 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=0XoSNhR/ASIgC29b1QcqzSACqNk99wrEhwjSvUDbz6c=; b=LSvJsO+/B8MK/xmdP9SdTKAr/9GUTxGhn6wmKLyc6pV1o3dKishqHavE/ci5Q+48V3 Bnl6rjrNb/S7hs05zIOP+DBI/FMq7LnbbhnTJ6juICfsMqAUbNmJhdR6ihrpXbA+01JC 4eIa3MFwb1n0ogLNS3xNYccQEfblqIVliqWAqalIpyFXV7b08zLe2PJtPfeOuEF8iOap aos/sAb+ipzPjoyaxR6LYYuzB7asHSxqmlecOOiKMF4s2M5Q24vnm6yZTM5DLVRqW/h1 1iBWmiUUEmcUNshjhy7MMuHWPpjwaFwinpiGkzqEI8QWVe+P5zMOSbJbYaH6qzgEoofT KmqA== X-Gm-Message-State: APjAAAW1L+aLTnV6eqLsGqEs8asZuj2HbD7Vig3YfNBbJrTctk5KXfi/ lbltxkKJ8IbwhKOXukQ4byY= X-Google-Smtp-Source: APXvYqxgxPxmJy4IeHukY/9neAMk58JMsreVeSXJGri+tBWS8g3JhfCE+V6EJMQYZANdY13bgj1coA== X-Received: by 2002:a17:902:bd06:: with SMTP id p6mr14968883pls.189.1562972601841; Fri, 12 Jul 2019 16:03:21 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id 137sm12366805pfz.112.2019.07.12.16.03.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Jul 2019 16:03:20 -0700 (PDT) Subject: Re: BUG: MAX_STACK_TRACE_ENTRIES too low! (2) To: Peter Zijlstra Cc: Eric Dumazet , Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org, syzbot , syzkaller-bugs@googlegroups.com References: <20190710172123.GC801@sol.localdomain> <20190710180242.GA193819@gmail.com> <47a9287d-1f02-95d5-a5cf-55f0c0d38378@gmail.com> <9219c421-0868-f97f-2d84-df48aed9f8a8@acm.org> <20190710220943.GM3419@hirez.programming.kicks-ass.net> <20190712085536.GP3402@hirez.programming.kicks-ass.net> From: Bart Van Assche Message-ID: Date: Fri, 12 Jul 2019 16:03:18 -0700 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: <20190712085536.GP3402@hirez.programming.kicks-ass.net> 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 7/12/19 1:55 AM, Peter Zijlstra wrote: > On Thu, Jul 11, 2019 at 11:53:12AM -0700, Bart Van Assche wrote: >> On 7/10/19 3:09 PM, Peter Zijlstra wrote: >>> One thing I mentioned when Thomas did the unwinder API changes was >>> trying to move lockdep over to something like stackdepot. >>> >>> We can't directly use stackdepot as is, because it uses locks and memory >>> allocation, but we could maybe add a lower level API to it and use that >>> under the graph_lock() on static storage or something. >>> >>> Otherwise we'll have to (re)implement something like it. >>> >>> I've not looked at it in detail. >> >> Hi Peter, >> >> Is something like the untested patch below perhaps what you had in mind? > > Most excellent, yes! Now I suppose the $64000 question is if it actually > reduces the amount of storage we use for stack traces.. > > Seems to boot just fine.. :-) Hi Peter, On my setup after some time the space occupied by stack traces stabilizes to the following: # grep stack /proc/lockdep_stats stack-trace entries: 169456 [max: 524288] number of stack traces: 9073 number of stack hash chains: 6980 I think these numbers show that there are some but not too many hash collisions (the code for the hash statistics was added after I e-mailed my patch). Bart.