From owner-freebsd-questions@FreeBSD.ORG Thu Jul 23 20:23:08 2009 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5E5101065673 for ; Thu, 23 Jul 2009 20:23:08 +0000 (UTC) (envelope-from freebsd-questions@m.gmane.org) Received: from ciao.gmane.org (main.gmane.org [80.91.229.2]) by mx1.freebsd.org (Postfix) with ESMTP id DAF7B8FC12 for ; Thu, 23 Jul 2009 20:23:07 +0000 (UTC) (envelope-from freebsd-questions@m.gmane.org) Received: from list by ciao.gmane.org with local (Exim 4.43) id 1MU4og-0002TY-L4 for freebsd-questions@freebsd.org; Thu, 23 Jul 2009 20:23:02 +0000 Received: from 78-1-153-243.adsl.net.t-com.hr ([78.1.153.243]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 23 Jul 2009 20:23:02 +0000 Received: from ivoras by 78-1-153-243.adsl.net.t-com.hr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 23 Jul 2009 20:23:02 +0000 X-Injected-Via-Gmane: http://gmane.org/ To: freebsd-questions@freebsd.org From: Ivan Voras Date: Thu, 23 Jul 2009 22:22:40 +0200 Lines: 51 Message-ID: References: <200907221157.n6MBvpKf028533@mp.cs.niu.edu> <20090723132200.4cf4002e@gumby.homeunix.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig4E7529443CA8D9956615188F" X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: 78-1-153-243.adsl.net.t-com.hr User-Agent: Thunderbird 2.0.0.22 (Windows/20090605) In-Reply-To: <20090723132200.4cf4002e@gumby.homeunix.com> X-Enigmail-Version: 0.96.0 Sender: news Subject: Re: ULE and Prescott question X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Jul 2009 20:23:08 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig4E7529443CA8D9956615188F Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable RW wrote: > On Wed, 22 Jul 2009 22:33:46 +0200 > Ivan Voras wrote: >=20 >> Scott Bennett wrote: >>> This is a curiousity question. I'm running 7.2-STABLE at >>> present on an old Inspiron XPS, which has a 3.4 GHz P4 Prescott >>> CPU. I have hyperthreading enabled in the kernel. The question >>> is: is there any appreciable performance difference to be expected >>> with this hardware setup between the ULE scheduler and the 4BSD >>> scheduler? Or does the fact that there is only one core eliminate >>> any difference in performance characteristics? >> I'd guess the second thing. It's not like there's cache to be shared >> between cores, etc.=20 >=20 > But with hyperthreading enabled, don't you have virtual CPUs sharing > L1 cache=20 Yes, > rather that cores sharing L2 cache, making the case for ULE > even stronger? If you're thinking about ULEs "soft-pinning" of processes to CPUs then I don't think so for two reasons: it's not like 4BSD forces processes ping-ponging everywhere - for 2 logical CPUs it's not that there's much choice of where to schedule a process - and thread switches between HTT logical CPUs is supposed to be cheap - I think since the L1 is shared, HTT cores have access to cached data from "the other" core for no cost. --------------enig4E7529443CA8D9956615188F Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkpoxpUACgkQldnAQVacBciYiACgpsIA46bDyU8zejev+6TCpRXv b5wAn3uoF5X8zYkQ2A0cGnCqxCRgUns8 =rMJL -----END PGP SIGNATURE----- --------------enig4E7529443CA8D9956615188F--