On Thu, Oct 04, 2012 at 07:49:32AM +0100, Viresh Kumar wrote:
On 22 September 2012 00:02, morten.rasmussen@arm.com wrote:
From: Morten Rasmussen morten.rasmussen@arm.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.
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 tixy@linaro.org 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 morten.rasmussen@arm.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);elsecpumask_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