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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 7F114C636CB for ; Sat, 17 Jul 2021 17:34:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 657EE61176 for ; Sat, 17 Jul 2021 17:34:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233227AbhGQRhh (ORCPT ); Sat, 17 Jul 2021 13:37:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232828AbhGQRhg (ORCPT ); Sat, 17 Jul 2021 13:37:36 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49B4EC061762; Sat, 17 Jul 2021 10:34:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description; bh=Q+wswcJYx0J9VCEjAaimzcbWFDFM+jrzkSVI1Om9YP8=; b=Tc2Xcyp4qDe5ONVs9DMy/VIAJD ssAl0+fC8J6etu6unlJcMMd3JNN6l7QhWNJ1XfNUIXTs68Xc3FVIW3Pal7XxAABWz/Jc1Y4cGhCbi tbsqc8l0dHe/mIMoI3N2sAbjqdPpw9ZXfepAmiDnygEDM2v+PF6F8DY1aceKxkAwZ51jZDYv9w1Ur ybo04EokT05dT+CyyTq3t8Zfa3qJ87IVAxj6NWxXu2r0Aone9aEk/4tVxnQWUUu855U0acx8kiiif 0SlPuvv/HfRPjDOQVuoI0LuDvm46vwYdpV5Os9tT02YpSQXSIabDLnsbWnuDHF5nKAjcFOIg5h1Sr 1UND7SwA==; Received: from [2601:1c0:6280:3f0::aefb] by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1m4oCw-006tgb-Na; Sat, 17 Jul 2021 17:34:34 +0000 Subject: Re: [patch 07/54] mm/slub: use stackdepot to save stack trace in objects To: Vlastimil Babka , Linus Torvalds , Christoph Hellwig Cc: Andrew Morton , Christoph Lameter , glittao@gmail.com, Joonsoo Kim , Linux-MM , mm-commits@vger.kernel.org, Pekka Enberg , David Rientjes , linux-xfs , Geert Uytterhoeven References: <20210707175950.eceddb86c6c555555d4730e2@linux-foundation.org> <20210708010747.zIP9yxsci%akpm@linux-foundation.org> <3eb0e8e4-adae-883d-1be9-a086f01197ff@suse.cz> From: Randy Dunlap Message-ID: <13030ef0-556d-ee79-196c-8a5f7443f2ed@infradead.org> Date: Sat, 17 Jul 2021 10:34:33 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <3eb0e8e4-adae-883d-1be9-a086f01197ff@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org On 7/16/21 3:37 PM, Vlastimil Babka wrote: > On 7/16/21 10:12 PM, Linus Torvalds wrote: >> On Fri, Jul 16, 2021 at 12:39 AM Christoph Hellwig wrote: >>> >>> This somewhat unexpectedly causes a crash when running the xfs/433 test >>> in xfstests for me. Reverting the commit fixes the problem: >> >> I don't see why that would be the case, but I'm inclined to revert >> that commit for another reason: the code doesn't seem to match the >> description of the commit. >> >> It used to be that CONFIG_SLUB_DEBUG was a config option that was >> harmless and that defaulted to 'y' because there was little downside. >> In fact, it's not just "default y", it doesn't even *ask* the user >> unless CONFIG_EXPERT is on. Because it was fairly harmless. And then >> SLOB_DEBUG_ON was that "do you actually want this code _enabled_". >> >> But now it basically force-enables that STACKDEPOT support too, and >> then instead of having an _optional_ CONFIG_STACKTRACE, you basically >> have that as being forced on you whether you want active debugging or >> not. >> >> Maybe that >> >> select STACKDEPOT if STACKTRACE_SUPPORT >> >> should have been >> >> select STACKDEPOT if STACKTRACE > > I recall we tried that and run into KConfig recursive dependency hell as > "config STACKDEPOT" does "select STACKTRACE", and after some attempts > ended up with the above. > >> because i\t used to be that CONFIG_STACKTRACE was somewhat unusual, >> and only enabled for special debug cases (admittedly "CONFIG_TRACING" >> likely meant that it was fairly widely enabled). >> >> In contrast, STACKTRACE_SUPPORT is basically "this architecture supports it". >> >> So now it seems STACKDEPOT is enabled basically unconditionally. > > It seemed rather harmless as it was just a bit of extra code. But it's > true Geert reports [1] unexpected memory usage which I would have only > expected if actual stacks started to be collected. So I guess we'll have > to look into that. > > [1] > https://lore.kernel.org/lkml/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/ > >> So I really don't see why it would cause that xfs issue, but I think >> there are multiple reasons to just go "Hmm" on that commit. >> >> Comments? >> >> Linus >> > There is also the matter of lib/stackdepot.c build errors on ARCH=arc: https://lore.kernel.org/lkml/202107150600.LkGNb4Vb-lkp@intel.com/ -- ~Randy