From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dario Faggioli <dario.faggioli@citrix.com>
Subject: Re: Xen on ARM IRQ latency and scheduler overhead
Date: Mon, 20 Feb 2017 12:40:06 +0100
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To: George Dunlap <george.dunlap@citrix.com>, Stefano Stabellini <sstabellini@kernel.org>
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On Mon, 2017-02-20 at 11:04 +0000, George Dunlap wrote:
> On 18/02/17 00:41, Stefano Stabellini wrote:
> >=20
> > On Fri, 17 Feb 2017, Dario Faggioli wrote:=09
> > > 	=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0cyclictest 1us	cycli=
ctest 1ms	cyclictest
> > > 100ms		=09
> > > (cycles)	Credit1	Credit2	Credit1	Cred
> > > it2	Credit1	Credit2	=09
> > > wakeup-avg	2429	2035	1980	1633=09
> > > 2535	1979	=09
> > > wakeup-max	14577	113682	15153	203136=09
> > > 12285	115164	=09
> >=20
> > I am not that familiar with the x86 side of things, but the 113682
> > and
> > 203136 look worrisome, especially considering that credit1 doesn't
> > have
> > them.
>=20
> Dario,
>=20
> Do you reckon those 'MAX' values could be the load balancer running
> (both for credit1 and credit2)?
>=20
If they were max-es of do_schedule, that would have been my first
guess. But not in this case, as the load balancer is never called
during wakeup (neither in Credit nor Credit2).

But I'm curious about what happen, and am going to investigate that. It
should not be too hard has: 1) looks reproducible on my (x86) testbox
that I have here; 2) since it's x86 I have tracing! :-P

Dario
--=20
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
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