From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754307AbaIHJtH (ORCPT ); Mon, 8 Sep 2014 05:49:07 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:40870 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754111AbaIHJtF (ORCPT ); Mon, 8 Sep 2014 05:49:05 -0400 Date: Mon, 8 Sep 2014 11:48:55 +0200 From: Peter Zijlstra To: Jiri Olsa Cc: Jiri Olsa , linux-kernel@vger.kernel.org, Andi Kleen , Arnaldo Carvalho de Melo , Corey Ashford , David Ahern , Frederic Weisbecker , Ingo Molnar , "Jen-Cheng(Tommy) Huang" , Namhyung Kim , Paul Mackerras , Stephane Eranian Subject: Re: [PATCH 1/9] perf: Remove redundant parent context check from context_equiv Message-ID: <20140908094855.GR3588@twins.programming.kicks-ass.net> References: <1408977943-16594-1-git-send-email-jolsa@kernel.org> <1408977943-16594-2-git-send-email-jolsa@kernel.org> <20140902105036.GH5806@worktop.ger.corp.intel.com> <20140908094348.GB1172@krava.brq.redhat.com> <20140908094548.GA6758@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="LXESt2jNC8oCvz8w" Content-Disposition: inline In-Reply-To: <20140908094548.GA6758@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --LXESt2jNC8oCvz8w Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 08, 2014 at 11:45:48AM +0200, Peter Zijlstra wrote: > On Mon, Sep 08, 2014 at 11:43:48AM +0200, Jiri Olsa wrote: > > On Tue, Sep 02, 2014 at 12:50:36PM +0200, Peter Zijlstra wrote: > > > On Mon, Aug 25, 2014 at 04:45:35PM +0200, Jiri Olsa wrote: > > > > As described in commit: > > > > 1f9a7268c67f perf: Do not allow optimized switch for non-cloned e= vents > > > > we dont allow optimized switch for non cloned contexts. > > > >=20 > > > > There's no need now to check if one of the context is parent > > > > of the other in context_equiv function. > > > >=20 > > >=20 > > > OK, so talk to me about that patch; it looks like you're slowly > > > reverting: 5a3126d4fe7c ("perf: Fix the perf context switch > > > optimization"). > > >=20 > > > So what exactly is the problem? I'm still jet-lagged and not seeing i= t. > >=20 > > the problem is, that we cannot allow non-cloned context > > to be part of the optimized switch for reasons explained > > in commit 1f9a7268c67f >=20 > The thing is; I don't understand those reasons. That commit log doesn't > explain. Ah wait, I finally see. I think we want to fix that exit path, not disallow the cloning. The thing is, by not allowing this optimization simple things like eg. pipe-test say very expensive. --LXESt2jNC8oCvz8w Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJUDXuHAAoJEHZH4aRLwOS6YpYQAKOBIyGA+NXl2Qy/XM0ZLQsD m9ycidPKnMV3YL3BXRzKq9AiCdnGJqa0CqAH3VvEm/P0CKRAA3jyT2EM7/+8iu2l 1j44mMT8GKY11yQrexYHZ7XPYCrWmkMg94K4WeDBEBicrrWWjnyTPNxJNtdb8krJ xpRkdC9MFg1jOnNJcsyfMEFS0XvE3dKdJ7Kw5tn7nJ/maIUo4ZF/Y0TZPZHclA7q HNqy98dZm3JX4bTu+LGaRTNQz+7K8x+ifulSsEx+7ao5iOdBdXycQEtt1joktTW5 YtGAfDj+dfxIB8wV1LqInZJ9ekKgXoIKffs78Qohmakjuy7GlJW3PQDIo/Uao79y w8mxKR6fPgGnEPCjgZxj2NuVx3d7XOI6hW+mU7NMCNoBD79PYKzCYOHQYgVHte4S Du/akGpoDrdlUANAopcAfHqESUYAZQ90BPLA4JvxXwrhreJkqTaJIIlUQxPjxIB0 +EmjQoavHTgFogC8w9gdaDsP9lUn/ZjXm4NrQrw/BaxJoH29mv6Lrl20Rom6fW3J pRyNu9pFxAP+TYwz901R29sT9w3/6+/z1LFD+ZUlHpnvJz9FQ2tXKeAtROxySXg6 klH7yogGt5uL5SLspbW2SSx9P+JsZQN7yXqYmJo7RL/V9tvJBNz09iGQffHYPlcf rcPRIVhkv0RpdBLz7XZd =HfVH -----END PGP SIGNATURE----- --LXESt2jNC8oCvz8w--