linux-kernel - Re: [Bugme-new] [Bug 15709] New: swapper page allocation failure

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Date:	Thu, 06 May 2010 17:30:38 -0400
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Robert Wimmer <kernel@...ceti.net>
Cc:	mst@...hat.com, Avi Kivity <avi@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	bugzilla-daemon@...zilla.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mel Gorman <mel@....ul.ie>, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [Bugme-new] [Bug 15709] New: swapper page allocation failure

Sorry. I've been caught up in work in the past few days.

I can certainly help with the soft lockup if you are able to supply
either a dump that includes all threads stuck in the NFS, or a (binary)
wireshark dump that shows the NFSv4 traffic between the client and
server around the time of the hang.

Cheers
  Trond

On Thu, 2010-05-06 at 23:19 +0200, Robert Wimmer wrote: 
> I don't know if someone is still interested in this
> but I think Trond isn't further interested because
> the last error was of cource a "page allocation
> failure" and not a "soft lookup" which Trond was
> trying to solve. But the patch was for 2.6.34 and
> the "soft lookup" comes up only with some 2.6.30 and
> maybe some 2.6.31 kernel versions. But the first error
> I reported was a "page allocation failure" which
> all kernels >= 2.6.32 produces with this configuration
> I use (NFSv4).
> 
> Michael suggested to first solve the "soft lookup"
> before further investigating the "page allocation
> failure". We know that the "soft lookup" only
> pop's up with NFSv4 and not v3. I really want to
> use v4 but since I'm not a kernel hacker someone
> must guide me what to try next.
> 
> I know that you're all have a lot of other work to
> do but if there're no ideas left what to do next
> it's maybe best to close the bug for now and I stay with
> kernel 2.6.30 for now or go back to NFS v3 if I
> upgrade to a newer kernel. Maybe the error will
> be fixed "by accident" in >= 2.6.35 ;-) 
> 
> Thanks!
> Robert
> 
> 
> 
> On 05/03/10 10:11, kernel@...ceti.net wrote:
> > Anything we can do to investigate this further?
> >
> > Thanks!
> > Robert
> >
> >
> > On Wed, 28 Apr 2010 00:56:01 +0200, Robert Wimmer <kernel@...ceti.net>
> > wrote:
> >   
> >> I've applied the patch against the kernel which I got
> >> from "git clone ...." resulted in a kernel 2.6.34-rc5.
> >>
> >> The stack trace after mounting NFS is here:
> >> https://bugzilla.kernel.org/attachment.cgi?id=26166
> >> /var/log/messages after soft lockup:
> >> https://bugzilla.kernel.org/attachment.cgi?id=26167
> >>
> >> I hope that there is any usefull information in there.
> >>
> >> Thanks!
> >> Robert
> >>
> >> On 04/27/10 01:28, Trond Myklebust wrote:
> >>     
> >>> On Tue, 2010-04-27 at 00:18 +0200, Robert Wimmer wrote: 
> >>>   
> >>>       
> >>>>> Sure. In addition to what you did above, please do
> >>>>>
> >>>>> mount -t debugfs none /sys/kernel/debug
> >>>>>
> >>>>> and then cat the contents of the pseudofile at
> >>>>>
> >>>>> /sys/kernel/debug/tracing/stack_trace
> >>>>>
> >>>>> Please do this more or less immediately after you've finished
> >>>>>           
> > mounting
> >   
> >>>>> the NFSv4 client.
> >>>>>   
> >>>>>       
> >>>>>           
> >>>> I've uploaded the stack trace. It was generated
> >>>> directly after mounting. Here are the stacks:
> >>>>
> >>>> After mounting:
> >>>> https://bugzilla.kernel.org/attachment.cgi?id=26153
> >>>> After the soft lockup:
> >>>> https://bugzilla.kernel.org/attachment.cgi?id=26154
> >>>> The dmesg output of the soft lockup:
> >>>> https://bugzilla.kernel.org/attachment.cgi?id=26155
> >>>>
> >>>>     
> >>>>         
> >>>>> Does your server have the 'crossmnt' or 'nohide' flags set, or does
> >>>>>           
> > it
> >   
> >>>>> use the 'refer' export option anywhere? If so, then we might have to
> >>>>> test further, since those may trigger the NFSv4 submount feature.
> >>>>>   
> >>>>>       
> >>>>>           
> >>>> The server has the following settings:
> >>>> rw,nohide,insecure,async,no_subtree_check,no_root_squash
> >>>>
> >>>> Thanks!
> >>>> Robert
> >>>>
> >>>>
> >>>>     
> >>>>         
> >>> That second trace is more than 5.5K deep, more than half of which is
> >>> socket overhead :-(((.
> >>>
> >>> The process stack does not appear to have overflowed, however that
> >>>       
> > trace
> >   
> >>> doesn't include any IRQ stack overhead.
> >>>
> >>> OK... So what happens if we get rid of half of that trace by forcing
> >>> asynchronous tasks such as this to run entirely in rpciod instead of
> >>> first trying to run in the process context?
> >>>
> >>> See the attachment...
> >>>
> >>>       
> 


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