From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: [PATCH] xen: preserve native TSC speed during
 migration between identical hosts
Date: Tue, 30 May 2017 11:27:05 +0200
Message-ID: <20170530092705.GC26792@aepfle.de>
References: <20170524142505.11460-1-olaf@aepfle.de>
 <20170524150940.GI18530@char.us.oracle.com>
 <20170524152503.GB6930@aepfle.de>
 <20170524153315.GO18530@char.us.oracle.com>
Mime-Version: 1.0
Content-Type: multipart/mixed; boundary="===============5328640413901394884=="
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <20170524153315.GO18530@char.us.oracle.com>
List-Unsubscribe: <https://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
 <mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <https://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
 <mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Errors-To: xen-devel-bounces@lists.xen.org
Sender: "Xen-devel" <xen-devel-bounces@lists.xen.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Wei Liu <wei.liu2@citrix.com>, xen-devel@lists.xen.org, Ian Jackson <ian.jackson@eu.citrix.com>, Jan Beulich <jbeulich@suse.com>, Andrew Cooper <andrew.cooper3@citrix.com>
List-Id: xen-devel@lists.xenproject.org


--===============5328640413901394884==
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="hOcCNbCCxyk/YU74"
Content-Disposition: inline


--hOcCNbCCxyk/YU74
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline

On Wed, May 24, Konrad Rzeszutek Wilk wrote:

> Is there some form of tests that they can run to verify and test
> that this is safe? Or perhaps this is something that is based on the kernel
> versions? Like 4.11 are safe, but 3.18 is not?

I'm not sure why you are asking for specific kernel versions.


But the test is simply to boot a HVM domU with 'tsc_mode=native' and
migrate it to a similar dom0. This fails with 3.12 and 4.4 based domU
kernels, with xen-4.7 as dom0. This pretty much ruins the plan.

So far I have not investigated why the domU on the remote side does not
get any cpu time, or why it makes no progress. But in the end the I
think only a hardware upgrade to TSC-scaling capable CPUs will avoid the
performance penalty due to the TSC emulation.
I do not have access to such hardware to verify it.


Olaf

--hOcCNbCCxyk/YU74
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iF0EARECAB0WIQSkRyP6Rn//f03pRUBdQqD6ppg2fgUCWS065QAKCRBdQqD6ppg2
flU4AJ9xkr1g29T37YcdtFIklzFCKmq72gCg5GHJ/nPscBF92WO4s7NFTNR1xp4=
=oLGP
-----END PGP SIGNATURE-----

--hOcCNbCCxyk/YU74--


--===============5328640413901394884==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: base64
Content-Disposition: inline

X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs
IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVuLm9yZwpodHRwczovL2xpc3RzLnhlbi5v
cmcveGVuLWRldmVsCg==

--===============5328640413901394884==--