Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932511AbbLBKQt (ORCPT <rfc822;w@1wt.eu>);
	Wed, 2 Dec 2015 05:16:49 -0500
Received: from mail-wm0-f45.google.com ([74.125.82.45]:37006 "EHLO
	mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1755237AbbLBKQq (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 2 Dec 2015 05:16:46 -0500
Date: Wed, 2 Dec 2015 11:16:43 +0100
From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Johannes Weiner <hannes@cmpxchg.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: memcg uncharge page counter mismatch
Message-ID: <20151202101643.GC25284@dhcp22.suse.cz>
References: <20151201133455.GB27574@bbox>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20151201133455.GB27574@bbox>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2287
Lines: 51

On Tue 01-12-15 22:34:55, Minchan Kim wrote:
> With new test on mmotm-2015-11-25-17-08, I saw below WARNING message
> several times. I couldn't see it with reverting new THP refcount
> redesign.

Just a wild guess. What prevents migration/compaction from calling
split_huge_page on thp zero page? There is VM_BUG_ON but it is not clear
whether you run with CONFIG_DEBUG_VM enabled.

Also, how big is the underflow?

> I will try to make reproducer when I have a time but not sure.
> Before that, I hope someone catches it up.
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1340 at mm/page_counter.c:26 page_counter_cancel+0x34/0x40()
> Modules linked in:
> CPU: 0 PID: 1340 Comm: madvise_test Not tainted 4.4.0-rc2-mm1-kirill+ #12
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  ffffffff81782eeb ffff880072b97be8 ffffffff8126f476 0000000000000000
>  ffff880072b97c20 ffffffff8103e476 ffff88006b35d0b0 00000000000001fe
>  0000000000000000 00000000000001fe ffff88006b35d000 ffff880072b97c30
> Call Trace:
>  [<ffffffff8126f476>] dump_stack+0x44/0x5e
>  [<ffffffff8103e476>] warn_slowpath_common+0x86/0xc0
>  [<ffffffff8103e56a>] warn_slowpath_null+0x1a/0x20
>  [<ffffffff8114c754>] page_counter_cancel+0x34/0x40
>  [<ffffffff8114c852>] page_counter_uncharge+0x22/0x30
>  [<ffffffff8114fe17>] uncharge_batch+0x47/0x140
>  [<ffffffff81150033>] uncharge_list+0x123/0x190
>  [<ffffffff8115222b>] mem_cgroup_uncharge_list+0x1b/0x20
>  [<ffffffff810fe9bb>] release_pages+0xdb/0x350
>  [<ffffffff8113044d>] free_pages_and_swap_cache+0x9d/0x120
>  [<ffffffff8111a546>] tlb_flush_mmu_free+0x36/0x60
>  [<ffffffff8111b63c>] tlb_finish_mmu+0x1c/0x50
>  [<ffffffff81125f38>] exit_mmap+0xd8/0x130
>  [<ffffffff8103bd56>] mmput+0x56/0xe0
>  [<ffffffff8103ff4d>] do_exit+0x1fd/0xaa0
>  [<ffffffff8104086f>] do_group_exit+0x3f/0xb0
>  [<ffffffff810408f4>] SyS_exit_group+0x14/0x20
>  [<ffffffff8142b617>] entry_SYSCALL_64_fastpath+0x12/0x6a
> ---[ end trace 7864cf719fb83e12 ]---

-- 
Michal Hocko
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/