netdev - Re: [Bugme-new] [Bug 16083] New: swapper: Page allocation failure

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Date:	Thu, 03 Jun 2010 23:13:23 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [Bugme-new] [Bug 16083] New: swapper: Page allocation failure

Le jeudi 03 juin 2010 à 13:02 -0700, Andrew Morton a écrit :
> On Mon, 31 May 2010 15:55:12 GMT
> bugzilla-daemon@...zilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=16083
> > 
> >            Summary: swapper: Page allocation failure
> >            Product: Memory Management
> >            Version: 2.5
> >     Kernel Version: 2.6.34
> >           Platform: All
> >         OS/Version: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: Other
> >         AssignedTo: akpm@...ux-foundation.org
> >         ReportedBy: sgunderson@...foot.com
> >         Regression: No
> > 
> > 
> > Hi,
> > 
> > Since upgrading from a Q9450 to 2xE5520 (and upgrading from 2.6.34-rc-something
> > to 2.6.34), I've started seeing these:
> > 
> > [605882.372418] swapper: page allocation failure. order:2, mode:0x4020
> > [605882.378981] Pid: 0, comm: swapper Not tainted 2.6.34 #1
> > [605882.384617] Call Trace:
> > [605882.387499]  <IRQ>  [<ffffffff81096d5a>] __alloc_pages_nodemask+0x5b0/0x629
> > [605882.395068]  [<ffffffff81096de5>] __get_free_pages+0x12/0x4f
> > [605882.401103]  [<ffffffff810bdeb4>] __kmalloc_track_caller+0x4c/0x156
> > [605882.407817]  [<ffffffff81245986>] ? sock_alloc_send_pskb+0xdd/0x32d
> > [605882.414556]  [<ffffffff8124a515>] __alloc_skb+0x66/0x15b
> 
> I wonder if we should switch __alloc_skb() over to __GFP_NOWARN. 
> People keep on reporting events such as the above, and nobody's
> getting any value from this.
> 

Then we could make __GFP_NOWARN for all allocations in kernel, why
network is so special ?

> Downsides:
> 
> - the change would tend to deprive MM developers of prompt "hey you
>   broke it again" notifications.
> 
> - if a system is getting enough allocation failures to impact
>   throughput, the operators won't *know* that it's happening, and so
>   they won't make the changes necessary to reduce the frequency of
>   memory allocation failures.
> 

We should have SNMP counter increments 

> If these are likely to be a problem, perhaps networking could provide
> some other form of "hey, you keep on running out of memory"
> notification, if it doesn't already do so.
> 
> Thoughts?
> 

order-2 ATOMIC allocations ?

skb = mld_newpack(dev, dev->mtu);

Let's face it : It can not work in the long term.

MTU=9000 on a system with 4K pages... Oh well...

maybe net/ipv6/mcast.c should cap dev->mtu to PAGE_SIZE-128 or
something, so that order-0 allocations are done.



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