linux-kernel - Re: [PATCH 00/31] numa/core patches

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Date:	Wed, 31 Oct 2012 00:26:30 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Johannes Weiner <hannes@...xchg.org>
cc:	Zhouping Liu <zliu@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Ingo Molnar <mingo@...nel.org>, CAI Qian <caiqian@...hat.com>
Subject: Re: [PATCH 00/31] numa/core patches

On Tue, 30 Oct 2012, Johannes Weiner wrote:
> On Tue, Oct 30, 2012 at 02:29:25PM +0800, Zhouping Liu wrote:
> > On 10/29/2012 01:56 AM, Johannes Weiner wrote:
> > >On Fri, Oct 26, 2012 at 11:08:00AM +0200, Peter Zijlstra wrote:
> > >>On Fri, 2012-10-26 at 17:07 +0800, Zhouping Liu wrote:
> > >>>[  180.918591] RIP: 0010:[<ffffffff8118c39a>]  [<ffffffff8118c39a>] mem_cgroup_prepare_migration+0xba/0xd0
> > >>>[  182.681450]  [<ffffffff81183b60>] do_huge_pmd_numa_page+0x180/0x500
> > >>>[  182.775090]  [<ffffffff811585c9>] handle_mm_fault+0x1e9/0x360
> > >>>[  182.863038]  [<ffffffff81632b62>] __do_page_fault+0x172/0x4e0
> > >>>[  182.950574]  [<ffffffff8101c283>] ? __switch_to_xtra+0x163/0x1a0
> > >>>[  183.041512]  [<ffffffff8101281e>] ? __switch_to+0x3ce/0x4a0
> > >>>[  183.126832]  [<ffffffff8162d686>] ? __schedule+0x3c6/0x7a0
> > >>>[  183.211216]  [<ffffffff81632ede>] do_page_fault+0xe/0x10
> > >>>[  183.293705]  [<ffffffff8162f518>] page_fault+0x28/0x30
> > >>Johannes, this looks like the thp migration memcg hookery gone bad,
> > >>could you have a look at this?
> > >Oops.  Here is an incremental fix, feel free to fold it into #31.
> > Hello Johannes,
> > 
> > maybe I don't think the below patch completely fix this issue, as I
> > found a new error(maybe similar with this):
> > 
> > [88099.923724] ------------[ cut here ]------------
> > [88099.924036] kernel BUG at mm/memcontrol.c:1134!
> > [88099.924036] invalid opcode: 0000 [#1] SMP
> > [88099.924036] Modules linked in: lockd sunrpc kvm_amd kvm
> > amd64_edac_mod edac_core ses enclosure serio_raw bnx2 pcspkr shpchp
> > joydev i2c_piix4 edac_mce_amd k8temp dcdbas ata_generic pata_acpi
> > megaraid_sas pata_serverworks usb_storage radeon i2c_algo_bit
> > drm_kms_helper ttm drm i2c_core
> > [88099.924036] CPU 7
> > [88099.924036] Pid: 3441, comm: stress Not tainted 3.7.0-rc2Jons+ #3
> > Dell Inc. PowerEdge 6950/0WN213
> > [88099.924036] RIP: 0010:[<ffffffff81188e97>] [<ffffffff81188e97>]
> > mem_cgroup_update_lru_size+0x27/0x30
> 
> Thanks a lot for your testing efforts, I really appreciate it.
> 
> I'm looking into it, but I don't expect power to get back for several
> days where I live, so it's hard to reproduce it locally.
> 
> But that looks like an LRU accounting imbalance that I wasn't able to
> tie to this patch yet.  Do you see weird numbers for the lru counters
> in /proc/vmstat even without this memory cgroup patch?  Ccing Hugh as
> well.

Sorry, I didn't get very far with it tonight.

Almost certain to be a page which was added to lru while it looked like
a 4k page, but taken off lru as a 2M page: we are taking a 2M page off
lru here, it's likely to be the page in question, but not necessarily.

There's quite a few put_page()s in do_huge_pmd_numa_page(), and it
would help if we could focus on the one which is giving the trouble,
but I don't know which that is.  Zhouping, if you can, please would
you do an "objdump -ld vmlinux >bigfile" of your kernel, then extract
from bigfile just the lines from "<do_huge_pmd_numa_page>:" to whatever
is the next function, and post or mail privately just that disassembly.
That should be good to identify which of the put_page()s is involved.

do_huge_pmd_numa_page() does look a bit worrying, but I've not pinned
the misaccounting seen to the aspects which have worried me so far.
Where is a check for page_mapcount(page) being 1?  And surely it's
unsafe to to be migrating the page when it was found !PageLRU?  It's
quite likely to be sitting in a pagevec or on a local list somewhere,
about to be added to lru at any moment.

Hugh
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