From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dario Faggioli <dario.faggioli@citrix.com>
Subject: Re: Xen 4.8 + Linux 4.9 + Credit2 = can't bootup
Date: Thu, 5 Jan 2017 09:39:15 +0100
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References: <20170105015203.GA11785@char.us.oracle.com>
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To: Andrew Cooper <andrew.cooper3@citrix.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, george.dunlap@eu.citrix.com, xen-devel@lists.xenproject.org, "anshul.makkar" <anshul.makkar@citrix.com>
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On Thu, 2017-01-05 at 02:05 +0000, Andrew Cooper wrote:
> On 05/01/2017 01:52, Konrad Rzeszutek Wilk wrote:
> > It works just fine with credit1 (see further down the log)
> > but if I try credit2 it ends up hanging during bootup.=C2=A0
> >=20
> > I am a going to naively assume it is due to how the vCPUs are
> > exposed (Where they match the physical CPUs under credit1),
> > but under credit2 they are different.
> >=20
> > The dom0_max_vcpus does not seem to have any affect. When I remove
> > it
> > things are still being problematic.
> >=20
> > Help!?
>=20
> This matches the symptoms seen by XenServer when trying to stress
> 32vcpu
> guests under Credit2.=C2=A0=C2=A0Malcolm did find (based on interpreted i=
perf
> throughput graphs) that Credit2 did seem to preferentially schedule
> the
> lower-number vcpus, rather than scheduling them evenly.
>=20
To be fair (and just for the records, since the cause seems actually to
be something else), this was with an old version (at least two Xen
releases ago, IIRC, certainly not 4.8) and known to be buggy version of
Credit2.

We have other tests and benchmarks, done on equally big machines which
proves the scheduler is 100% functional.

Regards,
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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