Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755767AbcJFLPq (ORCPT ); Thu, 6 Oct 2016 07:15:46 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:41177 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754586AbcJFLPk (ORCPT ); Thu, 6 Oct 2016 07:15:40 -0400 Date: Thu, 6 Oct 2016 13:13:08 +0200 (CEST) From: Thomas Gleixner To: Tim Chen cc: Srinivas Pandruvada , rjw@rjwysocki.net, mingo@redhat.com, bp@suse.de, x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, peterz@infradead.org, jolsa@redhat.com Subject: Re: [PATCH v5 5/9] x86/sysctl: Add sysctl for ITMT scheduling feature In-Reply-To: <1475684673.3916.299.camel@linux.intel.com> Message-ID: References: <1475322326-160112-1-git-send-email-srinivas.pandruvada@linux.intel.com> <1475322326-160112-6-git-send-email-srinivas.pandruvada@linux.intel.com> <1475684673.3916.299.camel@linux.intel.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: multipart/mixed; BOUNDARY="8323329-505336005-1475752388=:22338" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1847 Lines: 53 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-505336005-1475752388=:22338 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Wed, 5 Oct 2016, Tim Chen wrote: > On Wed, 2016-10-05 at 16:35 +0200, Thomas Gleixner wrote: > > > + if (itmt_supported) { > > > + itmt_sysctl_header = > > > + register_sysctl_table(itmt_root_table); > > > + if (!itmt_sysctl_header) { > > > + mutex_unlock(&itmt_update_mutex); > > > + return; > > So you now have a state of capable which cannot be enabled. Whats the > > point? > > For multi-socket system where ITMT is not enabled by default, the operator > can still decide to enable it via sysctl. With a sysctl which failed to be installed. Good luck with that. > > > + } > > > + /* > > > +  * ITMT capability automatically enables ITMT > > > +  * scheduling for small systems (single node). > > > +  */ > > > + if (topology_num_packages() == 1) > > > + sysctl_sched_itmt_enabled = 1; > > > + } else { > > > + if (itmt_sysctl_header) > > > + unregister_sysctl_table(itmt_sysctl_header); > > > + } > > > + > > > + if (sysctl_sched_itmt_enabled) { > > > + /* disable sched_itmt if we are no longer ITMT capable */ > > > + if (!itmt_supported) > > > > How do you get here if itmt is not supported?  > > If the OS decides to turn off ITMT for any reason, (i.e. invoke  > sched_set_itmt_support(false) after it has turned on itmt_support > before), this is the logic to do it.  We don't turn off ITMT support > after it has been turned on today, in the future the OS may. Then please make this two functions (set/clear) so one can actually follow the logic. The above is just too convoluted. Thanks, tglx --8323329-505336005-1475752388=:22338--