Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756884Ab2JDGte (ORCPT ); Thu, 4 Oct 2012 02:49:34 -0400 Received: from mail-ie0-f174.google.com ([209.85.223.174]:61386 "EHLO mail-ie0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755016Ab2JDGtc (ORCPT ); Thu, 4 Oct 2012 02:49:32 -0400 MIME-Version: 1.0 In-Reply-To: <1348252345-5642-7-git-send-email-morten.rasmussen@arm.com> References: <1348252345-5642-1-git-send-email-morten.rasmussen@arm.com> <1348252345-5642-7-git-send-email-morten.rasmussen@arm.com> Date: Thu, 4 Oct 2012 12:19:32 +0530 Message-ID: Subject: Re: [RFC PATCH 06/10] ARM: sched: Use device-tree to provide fast/slow CPU list for HMP From: Viresh Kumar To: morten.rasmussen@arm.com 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@arm.com, Amit Kucheria , Robin Randhawa Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4933 Lines: 139 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? > 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. > 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 -- 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/