From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: VCPU migration overhead conpensation ? Date: Wed, 10 Apr 2013 08:53:58 +0200 Message-ID: <1365576838.2934.7.camel@Abyss> References: <1365472000.9958.110.camel@Solace> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3661049860861804302==" Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Sisu Xi Cc: George Dunlap , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org --===============3661049860861804302== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-PnTw14rCaBxXJozZVwFo" --=-PnTw14rCaBxXJozZVwFo Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On mer, 2013-04-10 at 06:44 +0100, Sisu Xi wrote: > Hi, Dario: >=20 Hi! :-) > I am also performing some overhead measurement for the scheduler. If a > VCPU is migrated from one core to another, the overhead is around 2 > microseconds on my machine, which is much less than what is set in > Credit2 (50 microseconds).=20 >=20 Ok, and, finally, how did you decide to measure this? I mean, what is it that you are doing for coming up with that 2us value? When I was doing research on task scheduling, in "plain" OS, not hypervisors, I remember having setup something like this: you take a task (or a set of them), performing a known computation on a certain CPU, and you measure how long it takes. After that, you force a migration to another CPU, and keep monitoring the duration of the computation. Well, the first samples that you get right after the migration, gives you an idea of the overhead caused by the migration itself. Of course, you can/should try different kind of migrations, i.e., across cores (i.e., with a lot of shared caches), across sockets, etc. It is an indirect method, but the nice thing is you can use real programs and inspect the effect of migration on real workloads (e.g., a video player playing the same video). Of course, we have one more "layer of indirection" here (the vCPUs), but I guess we can think of something... So, again, I'm curious, how are you measuring it? Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-PnTw14rCaBxXJozZVwFo 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 v1.4.13 (GNU/Linux) iEYEABECAAYFAlFlDIYACgkQk4XaBE3IOsS/PACcCOWWYgqUaETXnAWwRdqP0tED YwwAn3lsTzsUOlqwnGHv8fzBCaa7elE1 =tlTG -----END PGP SIGNATURE----- --=-PnTw14rCaBxXJozZVwFo-- --===============3661049860861804302== 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 --===============3661049860861804302==--