From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754692AbaE1Pgk (ORCPT ); Wed, 28 May 2014 11:36:40 -0400 Received: from casper.infradead.org ([85.118.1.10]:43430 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218AbaE1Pgj (ORCPT ); Wed, 28 May 2014 11:36:39 -0400 Date: Wed, 28 May 2014 17:36:33 +0200 From: Peter Zijlstra To: Andi Kleen Cc: "Yan, Zheng" , linux-kernel@vger.kernel.org, mingo@elte.hu, eranian@google.com Subject: Re: [RFC PATCH 5/7] perf, x86: use the PEBS auto reload mechanism when possible Message-ID: <20140528153633.GZ11096@twins.programming.kicks-ass.net> References: <1401257890-30535-1-git-send-email-zheng.z.yan@intel.com> <1401257890-30535-6-git-send-email-zheng.z.yan@intel.com> <20140528075937.GO11096@twins.programming.kicks-ass.net> <20140528144643.GG29957@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="fXCyug6VAL2FbtaR" Content-Disposition: inline In-Reply-To: <20140528144643.GG29957@tassilo.jf.intel.com> 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 --fXCyug6VAL2FbtaR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, May 28, 2014 at 07:46:43AM -0700, Andi Kleen wrote: > On Wed, May 28, 2014 at 09:59:37AM +0200, Peter Zijlstra wrote: > > On Wed, May 28, 2014 at 02:18:08PM +0800, Yan, Zheng wrote: > > > When a fixed period is specified, this patch make perf use the PEBS > > > auto reload mechanism. This makes normal profiling faster, because > > > it avoids one costly MSR write in the PMI handler. > > >=20 > >=20 > > You can't do this unconditionally. Like I think you mention in the next > > patch, we need the PMI to fix up lots of cases. >=20 > There are two cases: >=20 > (1) Fixed period specified with PEBS. > The PMI still runs with threshold=3D1, but we can use the PEBS > auto-reload mechanism to automatically rewrite the counter which is > faster. >=20 > (2) Free running mode with more constraints >=20 > This is case (1) Sounds like something that should've been made clear in the Changelog. --fXCyug6VAL2FbtaR Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJThgKBAAoJEHZH4aRLwOS6pdIQAKQx3coUboLjlJwBCKapS99M UdGeUzEY1m/RIIWm7jGWgomWiE46xQa4PUT1pUw7xnFEVE8USlc5vshoJ5Ym2S3D fw41DfVY+2MThybgJWFL3whU3a1QCkGwSIWahSQZ0gk0X+xKa2RLVI+u14Tfjhpb tOfgKE74B2pyL5e8gal67LU+W79uTCVh9KQtnlbSjN3u8BJioRZdEpmATzUI5p82 lriZA3pRRmRtAMiTURGjSTLENpg7VBgxOQH2nzFmW18FunkNbUuuE+lQeb1FVITJ JtK8a33eC+wbjZETEKDPTiJRDwIFa1DQW12OxXKlaB+JraXX1UlHVLfnnN73/6hk 1sZENze2Wcb54iHCopuKA2l3WOPhEtequakVgS6WI3bwY93Ek9+l6cSY6R28QyHc WsYkQjUZ4Y5t+1FQjCQo7ZPxhYVAosRHJa9W+qM03n/CABO411CzKiqxEkk3G8SP Z/DWMGi02hv85Bbo4sMHwmpUPnv6L7wlNpu1RXBPVlANT9Dw7RRHEixIC5oM1irz sOwqq9x+9y0dNoXWsBFmCrZGBOURIUvwiJmJE1wpELHNA1lTUaqYwKCO32M1cqhi Ni+B/Sms7DrQ5QYV/IVUJmmjy3RUgakwSKFT8gM6lgQdAKUaK8sT3x60+haiO0FL HZqKM8n2cBqNAGUlBcuo =9uEu -----END PGP SIGNATURE----- --fXCyug6VAL2FbtaR--