Subject: Re: Kernel WARNING: at net/core/dev.c:1330
	__netif_schedule+0x2c/0x98()
From: Peter Zijlstra <peterz@infradead.org>
To: David Miller <davem@davemloft.net>
Cc: jarkao2@gmail.com, Larry.Finger@lwfinger.net, kaber@trash.net,
	torvalds@linux-foundation.org, akpm@linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-wireless@vger.kernel.org, mingo@redhat.com,
	nickpiggin@yahoo.com.au, paulmck@linux.vnet.ibm.com
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Date: Thu, 24 Jul 2008 12:08:56 +0200
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On Thu, 2008-07-24 at 02:32 -0700, David Miller wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Thu, 24 Jul 2008 11:27:05 +0200
> 
> > Well, not only lockdep, taking a very large number of locks is expensive
> > as well.
> 
> Right now it would be on the order of 16 or 32 for
> real hardware.
> 
> Much less than the scheduler currently takes on some
> of my systems, so currently you are the pot calling the
> kettle black. :-)

One nit, and then I'll let this issue rest :-)

The scheduler has a long lock dependancy chain (nr_cpu_ids rq locks),
but it never takes all of them at the same time. Any one code path will
at most hold two rq locks.