Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762380AbZAGWxk (ORCPT ); Wed, 7 Jan 2009 17:53:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751867AbZAGWx3 (ORCPT ); Wed, 7 Jan 2009 17:53:29 -0500 Received: from victor.provo.novell.com ([137.65.250.26]:50116 "EHLO victor.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751063AbZAGWx1 (ORCPT ); Wed, 7 Jan 2009 17:53:27 -0500 Message-ID: <4965331E.8090202@novell.com> Date: Wed, 07 Jan 2009 17:56:30 -0500 From: Gregory Haskins User-Agent: Thunderbird 2.0.0.18 (X11/20081112) MIME-Version: 1.0 To: Ingo Molnar CC: Andi Kleen , Matthew Wilcox , Linus Torvalds , Steven Rostedt , Peter Zijlstra , paulmck@linux.vnet.ibm.com, Chris Mason , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Nick Piggin , Peter Morreale , Sven Dietrich Subject: Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning References: <1231283778.11687.136.camel@twins> <1231329783.11687.287.camel@twins> <1231347442.11687.344.camel@twins> <20090107210923.GV2002@parisc-linux.org> <20090107213924.GP496@one.firstfloor.org> <49652C7C.3000909@novell.com> <20090107223317.GB27629@elte.hu> In-Reply-To: <20090107223317.GB27629@elte.hu> X-Enigmail-Version: 0.95.7 OpenPGP: id=D8195319 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig1059CEDB2C720EE9526EF1FD" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1959 Lines: 55 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig1059CEDB2C720EE9526EF1FD Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Ingo, Ingo Molnar wrote: > * Gregory Haskins wrote: > > =20 >> Can I ask a simple question in light of all this discussion? >> >> "Is get_task_struct() really that bad?" >> =20 > > it dirties a cacheline and it also involves atomics. > =20 Yes, understood. But we should note we are always going to be talking about thrashing caches here since we are ultimately having one CPU observe another. There's no way to get around that. I understand that there are various degrees of this occurring, and I have no doubt that the proposed improvements strive to achieve a reduction of that. My question is really targeted at "at what cost". Don't get me wrong. I am not advocating going back to get/put-task per se. I am simply asking the question of whether we have taken the design off into the weeds having lost sight of the actual requirements and/or results. Its starting to smell like we have. This is just a friendly reality check. Feel free to disregard. ;) -Greg --------------enig1059CEDB2C720EE9526EF1FD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEUEARECAAYFAkllMx4ACgkQlOSOBdgZUxlSVQCcC3fxtvKWwlIoUJuGkDJJWRSS 6pgAmMh9kAf9wrIq9+ppb/IIbTWvhSg= =B/yd -----END PGP SIGNATURE----- --------------enig1059CEDB2C720EE9526EF1FD-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/