From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id 473E91381F3 for ; Sat, 15 Dec 2012 12:43:12 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id AD69E21C0C7; Sat, 15 Dec 2012 12:42:53 +0000 (UTC) Received: from out4-smtp.messagingengine.com (out4-smtp.messagingengine.com [66.111.4.28]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id B01F321C0A2 for ; Sat, 15 Dec 2012 12:41:02 +0000 (UTC) Received: from compute2.internal (compute2.nyi.mail.srv.osa [10.202.2.42]) by gateway1.nyi.mail.srv.osa (Postfix) with ESMTP id 4E73C208D2 for ; Sat, 15 Dec 2012 07:41:02 -0500 (EST) Received: from frontend1.nyi.mail.srv.osa ([10.202.2.160]) by compute2.internal (MEProxy); Sat, 15 Dec 2012 07:41:02 -0500 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=binarywings.net; h=message-id:date:from:mime-version:to:subject:references :in-reply-to:content-type; s=mesmtp; bh=IvOdPYI3co41KG0S814FtQuA djw=; b=k9yQOu5xPrxQwv7sm/AePxKrKwNAm21UCcNj7KB9zGGWc5vSw+TryvMv +iwdIfp4/h6mMCXraolboV2oUhLaqnN1RVukyp9MnDi5YKatJ00rXC3dxP6rU5zy kipPFxq7wq6oxBC7cGsb2tjHLb30KyfaeT99gd1o7qXRkFhNDfw= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d= messagingengine.com; h=message-id:date:from:mime-version:to :subject:references:in-reply-to:content-type; s=smtpout; bh=IvOd PYI3co41KG0S814FtQuAdjw=; b=gbne7Fek9JxTX7iW0/NhjqE5P3Gf7H/C3hm2 4jRTlORTSbnZOr2mr37XBaX5/UEwvWXIUgCqptuCNlgZjAwDaTyr2PNTuPjt4WUp hLhcZC+kBGz0/NGe7Rl0vIjg72c3+1Wp5AiiJ4OwlrQ9qywHOIOJ8X7m3DkAqQTj gzoVfVw= X-Sasl-enc: UVk9Rllf8HLKtxIzDH4zcj57QansKFrZ7YeSgpA39Ju9 1355575261 Received: from [192.168.5.18] (unknown [83.169.5.6]) by mail.messagingengine.com (Postfix) with ESMTPA id 07C918E00AD for ; Sat, 15 Dec 2012 07:41:00 -0500 (EST) Message-ID: <50CC6FD6.1040601@binarywings.net> Date: Sat, 15 Dec 2012 13:40:54 +0100 From: Florian Philipp User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.11) Gecko/20121130 Thunderbird/10.0.11 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] Dual or Quad CPU complications? References: <20121213082346.7b6bae37@khamul.example.com> <50C98588.9080409@binarywings.net> In-Reply-To: X-Enigmail-Version: 1.3.5 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig4666FC922C299ACE1D1A8780" X-Archives-Salt: add3a65b-d5b8-42e7-bacc-2d8cb0e51638 X-Archives-Hash: 540c2462e577ce28d3b1816c38152df0 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig4666FC922C299ACE1D1A8780 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Am 15.12.2012 04:16, schrieb Grant: >> > >> > So if I have 2 physical CPU's with 4 cores each and I enable > SMP, I'm >> > >> > using >> > >> > 8 cores? Can NUMA be either enabled or disabled when using > more than >> > >> > one >> > >> > physical CPU, or is it required? >> > >> >> > >> >> > >> NUMA is a hardware architecture. It's how you access memory on a >> > >> hardware level: NUMA =3D Non Uniform Memory Access vs a UMA > architecture >> > >> of typical (old/legacy) SMP systems (UMA =3D Uniform Memory Acces= s). >> > >> >> > >> In a UMA system, all the memory belongs to all the sockets. In a = NUMA >> > >> system, each socket has it's "own" local memory. In modern (x86-6= 4) >> > >> processors, each socket has it's own memory controller so each so= cket >> > >> controls its own local memory. If one socket runs out of memory > it can >> > >> ask another socket to lend him some memory. In a UMA system, no > socket >> > >> has to ask since memory is global and belongs to all sockets so > if one >> > >> socket uses up all the memory ... the rest "starve". In NUMA, the= re's >> > >> more control over who uses what (be it cores or RAM). >> > >> >> > >> If you have a modern dual or quad (or higher #) socket system ...= >> > >> you've got NUMA architecture and you can't get rid of it, it's >> > >> hardware, not software. >> > > >> > > So I must enable CONFIG_NUMA for more than one physical CPU, and > disable it >> > > for only one physical CPU? >> > >> > >> > Yup. But ... Why would you want to disable a socket (CPU)? If you >> > disable a socket (CPU) ... you lose the memory attached to that sock= et >> > (CPU) not to mention you lose those cores ;) >> >> Sure but it sounds like if my system only has one CPU socket, > CONFIG_NUMA should be disabled. >=20 > I read this in make menuconfig: >=20 > "The kernel will try to allocate memory used by a CPU on the local > memory controller of the CPU and add some more NUMA awareness to the > kernel. For 64-bit this is recommended if the system is Intel Core > i7 (or later), AMD Opteron, or EM64T NUMA." >=20 > To be sure I have this right, I should disable CONFIG_NUMA on any syste= m > with a single physical CPU, even if it's an AMD Opteron? >=20 > - Grant Disable it. You only have one memory controller. There is nothing the kernel could do wrong without. Regards, Florian Philipp --------------enig4666FC922C299ACE1D1A8780 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlDMb9oACgkQqs4uOUlOuU9xSwCZARbKFvE22zcG2lUDIIzgHMBh VrYAnR6b8d8+hwZyxIYpxIb6g2QE25/N =j6nJ -----END PGP SIGNATURE----- --------------enig4666FC922C299ACE1D1A8780--