From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH] docs: Make note for the scheduler "cap" option warning about power management effects Date: Wed, 12 Jun 2013 10:41:23 +0200 Message-ID: <1371026483.20028.57.camel@Solace> References: <1370953898-10278-1-git-send-email-george.dunlap@eu.citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============3696354102292264422==" Return-path: In-Reply-To: <1370953898-10278-1-git-send-email-george.dunlap@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap Cc: Ian Jackson , Massimo Canonico , Ian Campbell , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org --===============3696354102292264422== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-Z3YL8u8bnWuGtkyWoASQ" --=-Z3YL8u8bnWuGtkyWoASQ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On mar, 2013-06-11 at 13:31 +0100, George Dunlap wrote: > Suggested-by: Massimo Canonico > Signed-off-by: George Dunlap > CC: Ian Campbell > CC: Ian Jackson > CC: Massimo Canonico > Reviewed-by: Dario Faggioli > --- > docs/man/xl.cfg.pod.5 | 13 +++++++++++++ > docs/man/xl.pod.1 | 13 +++++++++++++ > docs/man/xm.pod.1 | 13 +++++++++++++ > 3 files changed, 39 insertions(+) >=20 > diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5 > index b7d64a6..069b73f 100644 > --- a/docs/man/xl.cfg.pod.5 > +++ b/docs/man/xl.cfg.pod.5 > @@ -153,6 +153,19 @@ The cap is expressed in percentage of one physical C= PU: > The default, 0, means there is no upper cap. > Honoured by the credit and credit2 schedulers. > =20 > +NB: Many systems have features that will scale down the computing > +power of a cpu that is not 100% utilized. This can be in the > +operating system, but can also sometimes be below the operating system > +in the BIOS. If you set a cap such that individual cores are running > +at less than 100%, this may have an impact on the performance of your > +workload over and above the impact of the cap. For example, if your > +processor runs at 2GHz, and you cap a vm at 50%, the power management > +system may also reduce the clock speed to 1GHz; the effect will be > +that your VM gets 25% of the available power (50% of 1GHz) rather than > +50% (50% of 2GHz). If you are not getting the performance you expect, > +look at performance and cpufreq options in your operating system and > +your BIOS. > + > I'd have been less 'politically correct' toward BIOSes, but I guess that's me! :-P Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-Z3YL8u8bnWuGtkyWoASQ 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) iEYEABECAAYFAlG4NDMACgkQk4XaBE3IOsQS4QCfdrcd0zdU60XARm3cAByso1lg ri4AnRUmALqhTyNYd7nXmNHFwVYSa99J =kdtY -----END PGP SIGNATURE----- --=-Z3YL8u8bnWuGtkyWoASQ-- --===============3696354102292264422== 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 --===============3696354102292264422==--