Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751972AbcDUIE6 (ORCPT ); Thu, 21 Apr 2016 04:04:58 -0400 Received: from www.linutronix.de ([62.245.132.108]:47763 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751742AbcDUIEx (ORCPT ); Thu, 21 Apr 2016 04:04:53 -0400 Date: Thu, 21 Apr 2016 10:03:18 +0200 (CEST) From: Thomas Gleixner To: "Liang, Kan" cc: "peterz@infradead.org" , "linux-kernel@vger.kernel.org" , "ak@linux.intel.com" , "eranian@google.com" Subject: RE: [PATCH 1/1] perf/x86/intel/uncore: Add support for Intel SKL client uncore In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077058E426E@SHSMSX103.ccr.corp.intel.com> Message-ID: References: <1460708620-47969-1-git-send-email-kan.liang@intel.com> <37D7C6CF3E00A74B8858931C1DB2F077058E4102@SHSMSX103.ccr.corp.intel.com> <37D7C6CF3E00A74B8858931C1DB2F077058E426E@SHSMSX103.ccr.corp.intel.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1959 Lines: 44 On Wed, 20 Apr 2016, Liang, Kan wrote: > > On Wed, 20 Apr 2016, Liang, Kan wrote: > > > > The stop of the box1 events disables the whole machinery on that > > > > node and therefor the box0 event is wreckaged as well. Hmm? > > > > > > > Right. How about check the SKL_UNC_PERF_GLOBAL_CTL in enable_event? > > > If it's cleared, we can reset it there. The drawback is that there > > > will be an extra rdmsrl and a possible wrmsrl. > > > > Well, that does not buy anything as you cannot disable the thing at all, unless > > you have refcounting. And that refcounting needs to be in the 'type' > > struct and that would probably be some real pain to implement. > > > > The question is whether we need enable/disable at all. If the type is > > initialized we enable it and on exit we disable it. Ditto on cpu hotplug - which > > is also used for init to enable all nodes. > > > > So if there is no drawback in letting the thing enabled if no events are armed, > > then we really can do w/o the enable/disable_box callbacks. > > > There is no drawback in letting the thing enabled, but PERF_GLOBAL_CTL could > be disabled after Package C7. I add the enable/disable thing to try to > workaround it. I don't see how that solves it. If a counter is active, then C7 will stop it and you wont get anything useful from it after returning from C7. Or does an active counter prevent C7? > I once did the test on a SKL laptop. If the machine goes idle for a while, > then the uncore counter will always return 0. For fixing it, we have to > re-enable PERF_GLOBAL_CTL. Hmm, but that does only help for new events after returning from C7, right? > I think I made a typo in previous reply. I mean we can check it or just > force rewrite the PERF_GLOBAL_CTL in enable_box. We don't need disable_box > since there is no drawback in letting the thing enabled. Sure, but then you can just unconditionally enable it. IOW, leave the enable callback as is. Thanks, tglx