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,URIBL_BLOCKED,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 645AFC12002 for ; Fri, 16 Jul 2021 22:38:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 47056613EE for ; Fri, 16 Jul 2021 22:38:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232154AbhGPWlZ (ORCPT ); Fri, 16 Jul 2021 18:41:25 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:42878 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230227AbhGPWlY (ORCPT ); Fri, 16 Jul 2021 18:41:24 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id B829B1FD56; Fri, 16 Jul 2021 22:38:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1626475107; h=from:from:reply-to: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=QiZkom7aCM3xLpdHt0hB30lVzuPCzlDOb6gF6XnOuUE=; b=ESPCZ4bc4NB/hyHbq5a6CpkbCnBbMvqtE419cVBLHEVqRgk1RqWMCUHMOawgMRS1pyP+A1 PDRaeoVPhKtZlFIzqRqqsNWYwGXo6Q76k4sSM7lXqEs2hbUCgwO6iqCAENZQHGlKL6Q6jF rnCu+QqdhVXuzRDEG11XbPNipIbgY8I= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1626475107; h=from:from:reply-to: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=QiZkom7aCM3xLpdHt0hB30lVzuPCzlDOb6gF6XnOuUE=; b=rpaizg0krsnwjQCfQyfUki3ftA0gfVFGOz5+r4OQ+++fI51frhPgFzp5KQWa60UHKuIrnt q3Me/Vgrr38IsdBA== Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id 614B713B02; Fri, 16 Jul 2021 22:38:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id OY/PFWMK8mAPPQAAGKfGzw (envelope-from ); Fri, 16 Jul 2021 22:38:27 +0000 Subject: Re: [patch 07/54] mm/slub: use stackdepot to save stack trace in objects To: Linus Torvalds , Christoph Hellwig Cc: Andrew Morton , Christoph Lameter , glittao@gmail.com, Joonsoo Kim , Linux-MM , mm-commits@vger.kernel.org, Pekka Enberg , Randy Dunlap , David Rientjes , linux-xfs , Geert Uytterhoeven References: <20210707175950.eceddb86c6c555555d4730e2@linux-foundation.org> <20210708010747.zIP9yxsci%akpm@linux-foundation.org> From: Vlastimil Babka Message-ID: <3eb0e8e4-adae-883d-1be9-a086f01197ff@suse.cz> Date: Sat, 17 Jul 2021 00:37:57 +0200 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: 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 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 >