linux-kernel - Re: RFC: futex_wait() can DoS the tick

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Message-ID: <alpine.DEB.2.11.1506102024380.3786@nanos>
Date:	Wed, 10 Jun 2015 20:27:10 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: RFC: futex_wait() can DoS the tick

On Wed, 10 Jun 2015, Mike Galbraith wrote:
> Virgin source or kernels with zillion+ patches, doesn't matter.  To test
> virgin source earlier than EFI_STUB I had to pollute the source with
> EFI backports, but nothing else.
> 
> Just a sec while I check yet again that absolutely virgin master really
> really does stall....  Yup.  I pinned the tescase to CPU3..
> 
> LOC:       7432       5803       5418       6387       3371       3039       5757       3080   Local timer interrupts <== here
> LOC:       7560       6028       5632       6394       3538       3195       5937       3084   Local timer interrupts
> LOC:       7747       6135       5720       6394       3543       3262       6087       3086   Local timer interrupts
> LOC:       7930       6206       5785       6394       3571       3288       6303       3087   Local timer interrupts

So now it would be helpful to have a trace to see what CPU3 is
actually doing.

Thanks,

	tglx
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