Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932066Ab2JJKRw (ORCPT ); Wed, 10 Oct 2012 06:17:52 -0400 Received: from service87.mimecast.com ([91.220.42.44]:51457 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754804Ab2JJKRt convert rfc822-to-8bit (ORCPT ); Wed, 10 Oct 2012 06:17:49 -0400 Date: Wed, 10 Oct 2012 11:17:47 +0100 From: Morten Rasmussen To: Viresh Kumar Cc: "paulmck@linux.vnet.ibm.com" , "pjt@google.com" , "peterz@infradead.org" , "suresh.b.siddha@intel.com" , "linaro-sched-sig@lists.linaro.org" , "linaro-dev@lists.linaro.org" , "linux-kernel@vger.kernel.org" , Arvind Chauhan , Amit Kucheria , Robin Randhawa Subject: Re: [RFC PATCH 06/10] ARM: sched: Use device-tree to provide fast/slow CPU list for HMP Message-ID: <20121010101747.GD3729@e103034-lin> References: <1348252345-5642-1-git-send-email-morten.rasmussen@arm.com> <1348252345-5642-7-git-send-email-morten.rasmussen@arm.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginalArrivalTime: 10 Oct 2012 10:17:46.0936 (UTC) FILETIME=[7E805380:01CDA6D0] X-MC-Unique: 112101011174704501 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5991 Lines: 162 On Thu, Oct 04, 2012 at 07:49:32AM +0100, Viresh Kumar wrote: > On 22 September 2012 00:02, wrote: > > From: Morten Rasmussen > > > > We can't rely on Kconfig options to set the fast and slow CPU lists for > > HMP scheduling if we want a single kernel binary to support multiple > > devices with different CPU topology. E.g. TC2 (ARM's Test-Chip-2 > > big.LITTLE system), Fast Models, or even non big.LITTLE devices. > > > > This patch adds the function arch_get_fast_and_slow_cpus() to generate > > the lists at run-time by parsing the CPU nodes in device-tree; it > > assumes slow cores are A7s and everything else is fast. The function > > still supports the old Kconfig options as this is useful for testing the > > HMP scheduler on devices without big.LITTLE. > > But this code is handling this case too at the end, with following logic: > > > + cpumask_setall(fast); > > + cpumask_clear(slow); > > Am i missing something? > The HMP setup can be defined using Kconfig or DT. If both fails, it will set all cpus to be fast cpus and effectively disable SCHED_HMP. The Kconfig option is kept to allow testing of alternative HMP setups without having to change the DT or use DT at all which might be handy for non-ARM platforms. I hope that answers you question. > > This patch is reuse of a patch by Jon Medhurst with a > > few bits left out. > > Then probably he must be the author of this commit? Also a SOB is required > from him here. > I don't know what the correct procedure is for this sort of partial patch reuse. Since I didn't know better, I adopted Tixy's own reference style that he used in one of his patches which is an extension of a previous patch by me. I will of course fix it to follow normal procedure if there is one. > > Signed-off-by: Morten Rasmussen > > --- > > arch/arm/Kconfig | 4 ++- > > arch/arm/kernel/topology.c | 69 ++++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 72 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > > index cb80846..f1271bc 100644 > > --- a/arch/arm/Kconfig > > +++ b/arch/arm/Kconfig > > @@ -1588,13 +1588,15 @@ config HMP_FAST_CPU_MASK > > string "HMP scheduler fast CPU mask" > > depends on SCHED_HMP > > help > > - Specify the cpuids of the fast CPUs in the system as a list string, > > + Leave empty to use device tree information. > > + Specify the cpuids of the fast CPUs in the system as a list string, > > e.g. cpuid 0+1 should be specified as 0-1. > > > > config HMP_SLOW_CPU_MASK > > string "HMP scheduler slow CPU mask" > > depends on SCHED_HMP > > help > > + Leave empty to use device tree information. > > Specify the cpuids of the slow CPUs in the system as a list string, > > e.g. cpuid 0+1 should be specified as 0-1. > > > > diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c > > index 26c12c6..7682e12 100644 > > --- a/arch/arm/kernel/topology.c > > +++ b/arch/arm/kernel/topology.c > > @@ -317,6 +317,75 @@ void store_cpu_topology(unsigned int cpuid) > > cpu_topology[cpuid].socket_id, mpidr); > > } > > > > + > > +#ifdef CONFIG_SCHED_HMP > > + > > +static const char * const little_cores[] = { > > + "arm,cortex-a7", > > + NULL, > > +}; > > + > > +static bool is_little_cpu(struct device_node *cn) > > +{ > > + const char * const *lc; > > + for (lc = little_cores; *lc; lc++) > > + if (of_device_is_compatible(cn, *lc)) > > + return true; > > + return false; > > +} > > + > > +void __init arch_get_fast_and_slow_cpus(struct cpumask *fast, > > + struct cpumask *slow) > > +{ > > + struct device_node *cn = NULL; > > + int cpu = 0; > > + > > + cpumask_clear(fast); > > + cpumask_clear(slow); > > + > > + /* > > + * Use the config options if they are given. This helps testing > > + * HMP scheduling on systems without a big.LITTLE architecture. > > + */ > > + if (strlen(CONFIG_HMP_FAST_CPU_MASK) && strlen(CONFIG_HMP_SLOW_CPU_MASK)) { > > + if (cpulist_parse(CONFIG_HMP_FAST_CPU_MASK, fast)) > > + WARN(1, "Failed to parse HMP fast cpu mask!\n"); > > + if (cpulist_parse(CONFIG_HMP_SLOW_CPU_MASK, slow)) > > + WARN(1, "Failed to parse HMP slow cpu mask!\n"); > > + return; > > + } > > + > > + /* > > + * Else, parse device tree for little cores. > > + */ > > + while ((cn = of_find_node_by_type(cn, "cpu"))) { > > + > > + if (cpu >= num_possible_cpus()) > > + break; > > + > > + if (is_little_cpu(cn)) > > + cpumask_set_cpu(cpu, slow); > > + else > > + cpumask_set_cpu(cpu, fast); > > + > > + cpu++; > > + } > > + > > + if (!cpumask_empty(fast) && !cpumask_empty(slow)) > > + return; > > + > > + /* > > + * We didn't find both big and little cores so let's call all cores > > + * fast as this will keep the system running, with all cores being > > + * treated equal. > > + */ > > + cpumask_setall(fast); > > + cpumask_clear(slow); > > +} > > + > > +#endif /* CONFIG_SCHED_HMP */ > > All above calls to of_*() routines have dependency on CONFIG_OF > It would be very easy to blame someone else here... :) I will fix it. Thanks, Morten > -- > viresh > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/