From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f44.google.com (mail-wg0-f44.google.com [74.125.82.44]) by kanga.kvack.org (Postfix) with ESMTP id 9B93C6B009E for ; Sat, 7 Feb 2015 03:42:25 -0500 (EST) Received: by mail-wg0-f44.google.com with SMTP id z12so17673965wgg.3 for ; Sat, 07 Feb 2015 00:42:25 -0800 (PST) Received: from mail-wg0-x22f.google.com (mail-wg0-x22f.google.com. [2a00:1450:400c:c00::22f]) by mx.google.com with ESMTPS id dx7si6417167wib.26.2015.02.07.00.42.23 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 07 Feb 2015 00:42:24 -0800 (PST) Received: by mail-wg0-f47.google.com with SMTP id n12so17698136wgh.6 for ; Sat, 07 Feb 2015 00:42:23 -0800 (PST) MIME-Version: 1.0 Reply-To: sedat.dilek@gmail.com In-Reply-To: References: Date: Sat, 7 Feb 2015 09:42:23 +0100 Message-ID: Subject: Re: BUG: non-zero nr_pmds on freeing mm: 1 From: Sedat Dilek Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Pat Erley Cc: Linux-Next , kirill.shutemov@linux.intel.com, linux-mm , Johannes Weiner , Michal Hocko , Andrew Morton On Sat, Feb 7, 2015 at 8:33 AM, Sedat Dilek wrote: > On Sat, Feb 7, 2015 at 6:12 AM, Pat Erley wrote: >> I'm seeing the message in $subject on my Xen DOM0 on next-20150204 on >> x86_64. I haven't had time to bisect it, but have seen some discussion on >> similar topics here recently. I can trigger this pretty reliably by >> watching Netflix. At some point (minutes to hours) into it, the netflix >> video goes black (audio keeps going, so it still thinks it's working) and >> the error appears in dmesg. Refreshing the page gets the video going again, >> and it will continue playing for some indeterminate amount of time. >> >> Kirill, I've CC'd you as looking in the logs, you've patched a false >> positive trigger of this very recently(patch in kernel I'm running). Am I >> actually hitting a problem, or is this another false positive case? Any >> additional details that might help? >> >> Dmesg from system attached. > > [ CC some mm folks ] > > I have seen this, too. > > root# grep "BUG: non-zero nr_pmds on freeing mm:" /var/log/kern.log | wc -l > 21 > > Checking my logs: On next-20150203 and next-20150204. > > I am here not in a VM environment and cannot say what causes these messages. > I checked a bit the logs and commits in mm.git and linux-next.git. [1] lists: Kirill A. Shutemov (1): mm: do not use mm->nr_pmds on !MMU configurations NOTE: next-20150204 has this commit, but next-20150203 not (seen the BUG: line in both releases). Looking at Kirill's commit... At my 1st quick look I thought Kirill mixed mm_nr_pmds_init() in the case of defined(__PAGETABLE_PMD_FOLDED), but I was wrong. @@ -1440,13 +1440,15 @@ static inline int __pud_alloc(struct mm_struct *mm, pgd_t *pgd, ... #if defined(__PAGETABLE_PMD_FOLDED) || !defined(CONFIG_MMU) ... static inline void mm_nr_pmds_init(struct mm_struct *mm) { atomic_long_set(&mm->nr_pmds, 0); } ... #else ... static inline void mm_nr_pmds_init(struct mm_struct *mm) {} ... #endif So, I drop my idea of reverting Kirill's commit. Pat, not sure how often you build linux-next. When doing a daily linux-next testing... Before bisecting I normally checked which version of linux-next was the last good and which one was the first bad. I cannot say which strategy is better. But you seem to have a reliable test with watching Netflix. Regards, - Sedat - [1] http://git.kernel.org/cgit/linux/kernel/git/mhocko/mm.git/tag/?id=mmotm-2015-02-03-16-38 [2] http://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=e060ff1f1f00caab403bd208ffa78ed1b7ee0c4d -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org