actually cc'ing them this time. :)
On Fri, Jul 20, 2012 at 12:11 PM, Jon Medhurst (Tixy) <t...@linaro.org> wrote:
> Oops, I forgot to CC Viresh and Vincent on this, so resending...
> ---
>
> 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. ARM's TC2, 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.
>
> Signed-off-by: Jon Medhurst <t...@linaro.org>
> ---
>
> The reason I'm pushing this patch is that I want to use it for this
> month's Linaro vexpress release to help with the goal of having a single
> build which will work on all CoreTiles (and possibly Fast Models).
>
>
> arch/arm/kernel/topology.c | 69
> ++++++++++++++++++++++++++++++++++++++++++++
> kernel/sched/fair.c | 18 ++++--------
> 2 files changed, 75 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
> index f59193c..61302df 100644
> --- a/arch/arm/kernel/topology.c
> +++ b/arch/arm/kernel/topology.c
> @@ -287,6 +287,75 @@ 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 */
> +
> +
> /*
> * init_cpu_topology is called at boot when only one cpu is running
> * which prevent simultaneous write access to cpu_topology array
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index f705a87..e056361 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3084,25 +3084,19 @@ done:
>
> #ifdef CONFIG_SCHED_HMP
> /* Heterogenous multiprocessor (HMP) optimizations
> - * We need to know which cpus that are fast and slow. Ideally, this
> - * information would be provided by the platform in some way. For now
> it is
> - * set in the kernel config. */
> + * We need to know which cpus that are fast and slow. */
> static struct cpumask hmp_fast_cpu_mask;
> static struct cpumask hmp_slow_cpu_mask;
>
> -/* Setup fast and slow cpumasks.
> - * This should be setup based on device tree somehow. */
> +extern void __init arch_get_fast_and_slow_cpus(struct cpumask *fast,
> + struct cpumask *slow);
> +
> +/* Setup fast and slow cpumasks. */
> static int __init hmp_cpu_mask_setup(void)
> {
> char buf[64];
>
> - cpumask_clear(&hmp_fast_cpu_mask);
> - cpumask_clear(&hmp_slow_cpu_mask);
> -
> - if (cpulist_parse(CONFIG_HMP_FAST_CPU_MASK, &hmp_fast_cpu_mask))
> - WARN(1, "Failed to parse HMP fast cpu mask!\n");
> - if (cpulist_parse(CONFIG_HMP_SLOW_CPU_MASK, &hmp_slow_cpu_mask))
> - WARN(1, "Failed to parse HMP slow cpu mask!\n");
> + arch_get_fast_and_slow_cpus(&hmp_fast_cpu_mask, &hmp_slow_cpu_mask);
>
> printk(KERN_DEBUG "Initializing HMP scheduler:\n");
> cpulist_scnprintf(buf, 64, &hmp_fast_cpu_mask);
> --
> 1.7.10.4
>
>
>
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