From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dario Faggioli Subject: Re: [PATCH v2 3/7] x86: detect and initialize Intel CAT feature Date: Fri, 20 Mar 2015 10:24:44 +0000 Message-ID: <1426847083.2560.155.camel@citrix.com> References: <1426761695-12545-1-git-send-email-chao.p.peng@linux.intel.com> <1426761695-12545-4-git-send-email-chao.p.peng@linux.intel.com> <1426769087.2560.123.camel@citrix.com> <550ADEB6020000780006BA5B@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============4571864105120992737==" Return-path: In-Reply-To: <550ADEB6020000780006BA5B@mail.emea.novell.com> Content-Language: en-US List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "JBeulich@suse.com" Cc: Wei Liu , Ian Campbell , Andrew Cooper , "xen-devel@lists.xen.org" , "will.auld@intel.com" , Stefano Stabellini , "chao.p.peng@linux.intel.com" , Ian Jackson , "dgdegra@tycho.nsa.gov" , "Keir (Xen.org)" List-Id: xen-devel@lists.xenproject.org --===============4571864105120992737== Content-Language: en-US Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-ctUDPM1G4oteMu8R9q8C" --=-ctUDPM1G4oteMu8R9q8C Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2015-03-19 at 13:35 +0000, Jan Beulich wrote: > >>> On 19.03.15 at 13:44, wrote: > > On Thu, 2015-03-19 at 18:41 +0800, Chao Peng wrote: > >=20 > >> diff --git a/docs/misc/xen-command-line.markdown=20 > > b/docs/misc/xen-command-line.markdown > >> index 63871cb..768c55f 100644 > >> --- a/docs/misc/xen-command-line.markdown > >> +++ b/docs/misc/xen-command-line.markdown > >> @@ -1090,9 +1090,9 @@ This option can be specified more than once (up = to 8=20 > > times at present). > >> > `=3D ` > >> =20 > >> ### psr (Intel) > >> -> `=3D List of ( cmt: | rmid_max: )` > >> +> `=3D List of ( cmt: | rmid_max: | cat: |= =20 > > num_sockets: )` > >> > > As Tim, I also don't like the 'num_sockets' part of the interface. > >=20 > > Actually, I'm not sure I understand what the idea behind this parameter > > is. You say: > > =20 > >> +* Cache Alllocation Technology (Broadwell and later). Information re= garding > >> + the cache allocation. > >> + * `cat` instructs Xen to enable/disable Cache Allocation Technology= . > >> + * `num_sockets` indicates the number of available sockets for CAT f= eature > >> + detection. All the sockets up to num_sockets will be checked for = CAT > >> + feature.=20 > >> > > What it the use case of specifying, say, num_sockets=3D2, on a 4 socket > > system?=20 > >=20 > > Is it for making it possible for the user to disable the feature on som= e > > of the socket? If yes, I think it does make sense, but then why always > > the last ones? shouldn't this be a list of socket IDs? >=20 > I had asked about this before, and the answer was that this is to > _extend_ the range of sockets, to cover the CPU hotplug case.=20 > Ah... yes, hotplug is mentioned in the text. > But > of course I could see ways to at least default the count to something > reasonable even taking hotplug into account (like taking the boot > time CPUs-per-socket value and dividing nr_cpu_ids by that value). >=20 Indeed. I'm not that much a user of hotplug, but AFAICT, what's cool of it is that it is dynamic, and having to define this parameter upfront and/or then being limited by it is certainly suboptimal. Dario --=-ctUDPM1G4oteMu8R9q8C 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 iEYEABECAAYFAlUL9WsACgkQk4XaBE3IOsQWfQCgkuBBDzKdz/ToiqnCL+7HnLPK KSMAnj6i8Vg7+tKPAI3HlTfCvkrD0lpe =RV5A -----END PGP SIGNATURE----- --=-ctUDPM1G4oteMu8R9q8C-- --===============4571864105120992737== 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 --===============4571864105120992737==--