From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Pandruvada, Srinivas" Subject: Re: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error Date: Fri, 20 Nov 2015 23:57:56 +0000 Message-ID: <1448063875.9857.6.camel@intel.com> References: <1448022757-7856-1-git-send-email-prarit@redhat.com> <1448022757-7856-2-git-send-email-prarit@redhat.com> <20151120131833.GD3957@ubuntu> <564F37C8.60307@redhat.com> <20151120151944.GE3957@ubuntu> <564F3FBA.6030806@redhat.com> <1448049757.4914.3.camel@intel.com> <564FB111.5050403@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from mga11.intel.com ([192.55.52.93]:14494 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759681AbbKTX56 (ORCPT ); Fri, 20 Nov 2015 18:57:58 -0500 In-Reply-To: <564FB111.5050403@redhat.com> Content-Language: en-US Content-ID: <9206B1231F401C40B394C65E209C5399@intel.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "prarit@redhat.com" Cc: "Brown, Len" , "linux-kernel@vger.kernel.org" , "viresh.kumar@linaro.org" , "kristen@linux.intel.com" , "linux-pm@vger.kernel.org" , "rjw@rjwysocki.net" , "Yates, Alexandra" T24gRnJpLCAyMDE1LTExLTIwIGF0IDE4OjQ3IC0wNTAwLCBQcmFyaXQgQmhhcmdhdmEgd3JvdGU6 DQo+IA0KW2N1dF0NCj4gVGhlIC0xIGRpZmZlcmVuY2UgaGVyZSBpcyBub3QgdW5leHBlY3RlZCBn aXZlbiB0aGUgb3RoZXIgcHJvYmFibGUgcm91bmRpbmcNCj4gZXJyb3JzIGluIHRoZSBmcmVxdWVu Y3kgY29kZS4NClllcy4gSW50ZWwgUCBzdGF0ZSBjcHVmcmVxIGludGVyZmFjZSBpcyBub3Qgb3B0 aW1hbC4gV2UgZXZlbiBkZWJhdGUNCndoZXRoZXIgd2Ugc2hvdWxkIGhhdmUgdGhpcyBpbnRlcmZh Y2UgYXQgYWxsLg0KDQo+ICAgSSBoYXZlIGEgZmVlbGluZyB0aGF0IG5vIG9uZSByZWFsbHkgaGFz IGRvbmUgYW4NCj4gaW4gZGVwdGggcmV2aWV3IHRvIGZpbmQgdGhlIGVycm9ycy4gIEknbSBub3Qg Z29pbmcgdG8gYmVjYXVzZSBJJ20gcHJldHR5IHN1cmUNCj4gSS93ZSBjYW4gY29udmluY2UgdXNl cnMgdGhhdCAzMjAwID09IDMxOTkuOTggOykuICBGV0lXLCBJJ3ZlIGFsc28gd29uZGVyZWQgaWYN Cj4gdGhlIGRpZmZlcmVuY2UgYmV0d2VlbiB0aGUgbWFya2V0aW5nIGZyZXF1ZW5jeSBhbmQgdGhl IFRTQyBmcmVxdWVuY3kgKHdoaWNoIGluDQo+IHRoZW9yeSBlcXVhbHMgdGhlIG1hcmtldGluZyBm cmVxdWVuY3kpIGNhbiBjYXVzZSB0aGlzIHNvcnQgb2YgZXJyb3IuDQpXZSBkb24ndCBldmVuIHJl cXVlc3QgY29ycmVjdCBwc3RhdGUgaGVyZSwgc28gd2Ugd2lsbCBub3QgZ2V0IHRoYXQuIEJ1dA0K aW4gdGhpcyBjYXNlIGluIHR1cmJvIHJlZ2lvbiBpcyBub3QgY29udHJvbGxhYmxlIChhZnRlciBT YW5keWJyaWRnZSApDQphYm92ZSBzb21ldGhpbmcgY2FsbGVkIHR1cmJvIGFjdGl2YXRpb24gcmF0 aW8uIFNvIG5vdCBhIGJpZyBkZWFsLg0KQXMgbG9uZyBhcyB3ZSBjYW4gc2V0IGF0IGxvd2VyIGVu ZCB3ZSBhcmUgZmluZS4NCj4gDQoNClRoYW5rcywNClNyaW5pdmFzDQoNCj4gT09DIGRpZCB5b3Ug dHJ5IGxvYWRpbmcgdGhlIHN5c3RlbSBkb3duICh3aXRoIGEga2VybmVsIGJ1aWxkKSBhbmQgc3dp dGNoaW5nDQo+IGJldHdlZW4gZnJlcXVlbmNpZXM/ICBUaGF0J3MgYSBnb29kIHdheSB0byBzZWUg dGhlIGVmZmVjdCBvZiB0aGUgdHVyYm8gc3RhdGVzLg0KPiBJIHdvdWxkIGV4cGVjdCB0aGF0IHRo ZSB0dXJibyBzdGF0ZSBoaXRzIGEgbWF4aW11bSBvZiBhYm91dCA3NSUgb2YgdGhlIG1heCB0dXJi bw0KPiBzdGF0ZSB2YWx1ZSAoYmFzZWQgb24gZXhwZXJpbWVudCkgc28gdGhlIGRpZmZlcmVuY2Vz IHNob3VsZCBiZSBsYXJnZXIgYXQgdGhlDQo+IGhpZ2ggZW5kLg0KPiANCj4gUC4NCg0K From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760744AbbKTX6A (ORCPT ); Fri, 20 Nov 2015 18:58:00 -0500 Received: from mga11.intel.com ([192.55.52.93]:14494 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759681AbbKTX56 (ORCPT ); Fri, 20 Nov 2015 18:57:58 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,325,1444719600"; d="scan'208";a="843854196" From: "Pandruvada, Srinivas" To: "prarit@redhat.com" CC: "Brown, Len" , "linux-kernel@vger.kernel.org" , "viresh.kumar@linaro.org" , "kristen@linux.intel.com" , "linux-pm@vger.kernel.org" , "rjw@rjwysocki.net" , "Yates, Alexandra" Subject: Re: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error Thread-Topic: [PATCH 1/2] cpufreq, intel_pstate, Fix limits->max_policy_pct rounding error Thread-Index: AQHRI4+T2KWs1QhTd0qXMTHBhOp3NZ6lauaAgAAfIwCAAAK4AIAABsEAgABISYCAAD7TgIAAAuuA Date: Fri, 20 Nov 2015 23:57:56 +0000 Message-ID: <1448063875.9857.6.camel@intel.com> References: <1448022757-7856-1-git-send-email-prarit@redhat.com> <1448022757-7856-2-git-send-email-prarit@redhat.com> <20151120131833.GD3957@ubuntu> <564F37C8.60307@redhat.com> <20151120151944.GE3957@ubuntu> <564F3FBA.6030806@redhat.com> <1448049757.4914.3.camel@intel.com> <564FB111.5050403@redhat.com> In-Reply-To: <564FB111.5050403@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.254.182.10] Content-Type: text/plain; charset="utf-8" Content-ID: <9206B1231F401C40B394C65E209C5399@intel.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id tAKNw6mB004766 On Fri, 2015-11-20 at 18:47 -0500, Prarit Bhargava wrote: > [cut] > The -1 difference here is not unexpected given the other probable rounding > errors in the frequency code. Yes. Intel P state cpufreq interface is not optimal. We even debate whether we should have this interface at all. > I have a feeling that no one really has done an > in depth review to find the errors. I'm not going to because I'm pretty sure > I/we can convince users that 3200 == 3199.98 ;). FWIW, I've also wondered if > the difference between the marketing frequency and the TSC frequency (which in > theory equals the marketing frequency) can cause this sort of error. We don't even request correct pstate here, so we will not get that. But in this case in turbo region is not controllable (after Sandybridge ) above something called turbo activation ratio. So not a big deal. As long as we can set at lower end we are fine. > Thanks, Srinivas > OOC did you try loading the system down (with a kernel build) and switching > between frequencies? That's a good way to see the effect of the turbo states. > I would expect that the turbo state hits a maximum of about 75% of the max turbo > state value (based on experiment) so the differences should be larger at the > high end. > > P. {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I