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Date: Wed, 05 Mar 2014 22:38:52 +0000
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"mingo@...nel.org" <mingo@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"tony.luck@...el.com" <tony.luck@...el.com>,
"fenghua.yu@...el.com" <fenghua.yu@...el.com>,
"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>,
"james.hogan@...tec.com" <james.hogan@...tec.com>,
"cmetcalf@...era.com" <cmetcalf@...era.com>,
"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
"linux@....linux.org.uk" <linux@....linux.org.uk>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
CC: "preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>
Subject: Re: [RFC 6/6] sched: ARM: create a dedicated scheduler topology table
On 05/03/14 07:18, Vincent Guittot wrote:
> Create a dedicated topology table for ARM which will create new level to
> differentiate CPUs that can or not powergate independantly from others.
>
> The patch gives an example of how to add domain that will take advantage of
> SD_SHARE_POWERDOMAIN.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
> arch/arm/kernel/topology.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
> index 0bc94b1..ae8ffbc 100644
> --- a/arch/arm/kernel/topology.c
> +++ b/arch/arm/kernel/topology.c
> @@ -185,6 +185,15 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
> return &cpu_topology[cpu].core_sibling;
> }
>
> +/*
> + * The current assumption is that we can power gate each core independently.
> + * This will be superseded by DT binding once available.
> + */
> +const struct cpumask *cpu_corepower_mask(int cpu)
> +{
> + return &cpu_topology[cpu].thread_sibling;
> +}
Although you already explained this to me in a private conversation,
it's important to notice that running this set-up on a dual cluster TC2
(2 Cortex A15 - 3 Cortex A7) (no independent core power gating) we
don't see the SD_SHARE_POWERDOMAIN topology flag set in the sd's on MC
level because this patch-set doesn't contain the appropriate DT
parsing. Like you said back then, the comment above mentions this.
> +
> static void update_siblings_masks(unsigned int cpuid)
> {
> struct cputopo_arm *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
> @@ -266,6 +275,20 @@ void store_cpu_topology(unsigned int cpuid)
> cpu_topology[cpuid].socket_id, mpidr);
> }
>
> +static struct sched_domain_topology_level arm_topology[] = {
> +#ifdef CONFIG_SCHED_MC
> + { cpu_corepower_mask, SD_SHARE_PKG_RESOURCES | SD_SHARE_POWERDOMAIN, SD_INIT_NAME(GMC) },
> + { cpu_coregroup_mask, SD_SHARE_PKG_RESOURCES, SD_INIT_NAME(MC) },
> +#endif
> + { cpu_cpu_mask, SD_INIT_NAME(DIE) },
> + { NULL, },
> +};
> +
> +static void __init set_sched_topology(void)
> +{
> + sched_domain_topology = arm_topology;
> +}
> +
> /*
> * init_cpu_topology is called at boot when only one cpu is running
> * which prevent simultaneous write access to cpu_topology array
> @@ -289,4 +312,7 @@ void __init init_cpu_topology(void)
> smp_wmb();
>
> parse_dt_topology();
> +
> + /* Set scheduler topology descriptor */
> + set_sched_topology();
> }
>
How about the core scheduler provides an interface set_sched_topology()
instead of each arch has its own __init function? Sketched out below
for ARM.
-- >8 --
Subject: [PATCH] sched: set_sched_topology() as an interface of core scheduler
---
arch/arm/kernel/topology.c | 7 +------
include/linux/sched.h | 2 +-
kernel/sched/core.c | 5 +++++
3 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index ae8ffbc..89d5592 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -284,11 +284,6 @@ static struct sched_domain_topology_level arm_topology[] = {
{ NULL, },
};
-static void __init set_sched_topology(void)
-{
- sched_domain_topology = arm_topology;
-}
-
/*
* init_cpu_topology is called at boot when only one cpu is running
* which prevent simultaneous write access to cpu_topology array
@@ -314,5 +309,5 @@ void __init init_cpu_topology(void)
parse_dt_topology();
/* Set scheduler topology descriptor */
- set_sched_topology();
+ set_sched_topology(arm_topology);
}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8831413..fefd4e7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -998,7 +998,7 @@ struct sched_domain_topology_level {
#endif
};
-extern struct sched_domain_topology_level *sched_domain_topology;
+extern void set_sched_topology(struct sched_domain_topology_level *tl);
#ifdef CONFIG_SCHED_DEBUG
# define SD_INIT_NAME(type) .name = #type
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b4fb0df..a748c92 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6105,6 +6105,11 @@ static struct sched_domain_topology_level default_topology[] = {
struct sched_domain_topology_level *sched_domain_topology = default_topology;
+void set_sched_topology(struct sched_domain_topology_level *tl)
+{
+ sched_domain_topology = tl;
+}
+
#define for_each_sd_topology(tl) \
for (tl = sched_domain_topology; tl->mask; tl++)
--
1.8.3.2
--
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