From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: Virt overehead with HT [was: Re: Xen 4.5 development update] Date: Mon, 14 Jul 2014 18:44:43 +0200 Message-ID: <1405356283.7341.5.camel@Abyss> References: <20140701164347.61662A7843@laptop.dumpdata.com> <1405354372.29306.687.camel@Solace> <53C4062A.3040403@bobich.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============5976615134839875786==" Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1X6jMv-0008Ae-OZ for xen-devel@lists.xenproject.org; Mon, 14 Jul 2014 16:44:49 +0000 In-Reply-To: <53C4062A.3040403@bobich.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Gordan Bobic Cc: Lars Kurth , George Dunlap , Ross Lagerwall , "stefano.stabellini@citrix.com" , "xen-devel@lists.xenproject.org" List-Id: xen-devel@lists.xenproject.org --===============5976615134839875786== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-ABbcUOMeyHP2CAXHejb+" --=-ABbcUOMeyHP2CAXHejb+ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2014-07-14 at 17:32 +0100, Gordan Bobic wrote: > On 07/14/2014 05:12 PM, Dario Faggioli wrote: > > Elapsed(stddev) BAREMETAL HVM > > kernbench -j4 31.604 (0.0963328) 34.078 (0.168582) > > kernbench -j8 26.586 (0.145705) 26.672 (0.0432435) > > kernbench -j 27.358 (0.440307) 27.49 (0.364897) > > > > With HT disabled in BIOS (which means only 4 CPUs for both): > > Elapsed(stddev) BAREMETAL HVM > > kernbench -j4 57.754 (0.0642651) 56.46 (0.0578792) > > kernbench -j8 31.228 (0.0775887) 31.362 (0.210998) > > kernbench -j 32.316 (0.0270185) 33.084 (0.600442) >=20 BTW, there's a mistake here. The three runs, in the no-HT case are as follows: kernbench -j2 kernbench -j4 kernbench -j I.e., half the number of VCPUs, as much as there are VCPUs and unlimited, exactly as for the HT case. The numbers are the right one. > Just to make sure I'm reading this right - _disabling_ HT causes a near= =20 > 50% performance drop? >=20 For kernbench, and if you consider the "-j " run, yes, nearly. And that is both for baremetal and HVM guest. And with baremetal, I mean just bare Linux, no Xen at all involved. Doesn't this make sense? Well, perhaps the wrong indication I gave about the actual number of jobs used was misleading... better now? BTW, the idea here was to compare perf between baremetal and HVM, and they appear to be consistent. Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-ABbcUOMeyHP2CAXHejb+ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEABECAAYFAlPECPsACgkQk4XaBE3IOsQE/QCbBopIjqEDGm+S03P0/iodqu1m d9IAn1PXiAmvY8nXicM2DqOCZesXk9ui =teo8 -----END PGP SIGNATURE----- --=-ABbcUOMeyHP2CAXHejb+-- --===============5976615134839875786== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============5976615134839875786==--