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Date: Wed, 10 Oct 2012 12:29:34 +0100
From: "Jon Medhurst (Tixy)" <tixy@...aro.org>
To: Morten Rasmussen <Morten.Rasmussen@....com>
Cc: "linaro-sched-sig@...ts.linaro.org"
<linaro-sched-sig@...ts.linaro.org>,
"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"pjt@...gle.com" <pjt@...gle.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"suresh.b.siddha@...el.com" <suresh.b.siddha@...el.com>,
"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 06/10] ARM: sched: Use device-tree to provide
fast/slow CPU list for HMP
On Wed, 2012-10-10 at 12:04 +0100, Morten Rasmussen wrote:
> Hi Tixy,
>
> Could you have a look at my code stealing patch below? Since it is
> basically a trimmed version of one of your patches I would prefer to
> put you as author and have your SOB on it. What is your opinion?
Yes, I can agree with that opinion, (and my employer likes to count
their patch totals ;-) so please feel free to add:
From: Jon Medhurst <tixy@...aro.org>
Signed-off-by: Jon Medhurst <tixy@...aro.org>
Thanks
--
Tixy
> Thanks,
> Morten
>
> On Fri, Sep 21, 2012 at 07:32:21PM +0100, Morten Rasmussen wrote:
> > From: Morten Rasmussen <morten.rasmussen@....com>
> >
> > 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.
> >
> > This patch is reuse of a patch by Jon Medhurst <tixy@...aro.org> with a
> > few bits left out.
> >
> > Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
> > ---
> > 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 */
> > +
> > +
> > /*
> > * init_cpu_topology is called at boot when only one cpu is running
> > * which prevent simultaneous write access to cpu_topology array
> > --
> > 1.7.9.5
> >
>
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