[1/4] arm: topology: remove cpu_efficiency

Message ID 20170830144120.9312-2-dietmar.eggemann@arm.com
State New
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  • [1/4] arm: topology: remove cpu_efficiency
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Commit Message

Dietmar Eggemann Aug. 30, 2017, 2:41 p.m.
Remove the 'cpu_efficiency/clock-frequency dt property' based solution
to set cpu capacity which was only working for Cortex-A15/A7 arm
big.LITTLE systems.

I.e. the 'capacity-dmips-mhz' based solution is now the only one. It is
shared between arm and arm64 and works for every big.LITTLE system no
matter which core types it consists of.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

---
 arch/arm/kernel/topology.c | 113 ++-------------------------------------------
 1 file changed, 3 insertions(+), 110 deletions(-)

-- 
2.11.0

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Comments

Vincent Guittot Sept. 4, 2017, 7:49 a.m. | #1
Hi Dietmar,

Removing cpu effificiency table looks good to me. Nevertheless, i have
some comments below for this patch.

On 30 August 2017 at 16:41, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:
> Remove the 'cpu_efficiency/clock-frequency dt property' based solution

> to set cpu capacity which was only working for Cortex-A15/A7 arm

> big.LITTLE systems.

>

> I.e. the 'capacity-dmips-mhz' based solution is now the only one. It is

> shared between arm and arm64 and works for every big.LITTLE system no

> matter which core types it consists of.

>

> Cc: Russell King <linux@arm.linux.org.uk>

> Cc: Vincent Guittot <vincent.guittot@linaro.org>

> Cc: Juri Lelli <juri.lelli@arm.com>

> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

> ---

>  arch/arm/kernel/topology.c | 113 ++-------------------------------------------

>  1 file changed, 3 insertions(+), 110 deletions(-)

>

> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c

> index bf949a763dbe..04ccfdd94213 100644

> --- a/arch/arm/kernel/topology.c

> +++ b/arch/arm/kernel/topology.c

> @@ -47,52 +47,10 @@

>   */

>

>  #ifdef CONFIG_OF

> -struct cpu_efficiency {

> -       const char *compatible;

> -       unsigned long efficiency;

> -};

> -

> -/*

> - * Table of relative efficiency of each processors

> - * The efficiency value must fit in 20bit and the final

> - * cpu_scale value must be in the range

> - *   0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2

> - * in order to return at most 1 when DIV_ROUND_CLOSEST

> - * is used to compute the capacity of a CPU.

> - * Processors that are not defined in the table,

> - * use the default SCHED_CAPACITY_SCALE value for cpu_scale.

> - */

> -static const struct cpu_efficiency table_efficiency[] = {

> -       {"arm,cortex-a15", 3891},

> -       {"arm,cortex-a7",  2048},

> -       {NULL, },

> -};

> -

> -static unsigned long *__cpu_capacity;

> -#define cpu_capacity(cpu)      __cpu_capacity[cpu]

> -

> -static unsigned long middle_capacity = 1;

> -static bool cap_from_dt = true;

> -

> -/*

> - * Iterate all CPUs' descriptor in DT and compute the efficiency

> - * (as per table_efficiency). Also calculate a middle efficiency

> - * as close as possible to  (max{eff_i} - min{eff_i}) / 2

> - * This is later used to scale the cpu_capacity field such that an

> - * 'average' CPU is of middle capacity. Also see the comments near

> - * table_efficiency[] and update_cpu_capacity().

> - */

>  static void __init parse_dt_topology(void)

>  {

> -       const struct cpu_efficiency *cpu_eff;

> -       struct device_node *cn = NULL;

> -       unsigned long min_capacity = ULONG_MAX;

> -       unsigned long max_capacity = 0;

> -       unsigned long capacity = 0;

> -       int cpu = 0;

> -

> -       __cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),

> -                                GFP_NOWAIT);

> +       struct device_node *cn;

> +       int cpu;

>

>         cn = of_find_node_by_path("/cpus");

>         if (!cn) {

> @@ -101,9 +59,6 @@ static void __init parse_dt_topology(void)

>         }

>

>         for_each_possible_cpu(cpu) {

> -               const u32 *rate;

> -               int len;

> -

>                 /* too early to use cpu->of_node */

>                 cn = of_get_cpu_node(cpu, NULL);

>                 if (!cn) {

> @@ -115,73 +70,13 @@ static void __init parse_dt_topology(void)

>                         of_node_put(cn);

>                         continue;


AFAICT, this continue is now useless as it was there to skipe the cpu
table efficiency method

>                 }

> -

> -               cap_from_dt = false;

> -

> -               for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)

> -                       if (of_device_is_compatible(cn, cpu_eff->compatible))

> -                               break;

> -

> -               if (cpu_eff->compatible == NULL)

> -                       continue;

> -

> -               rate = of_get_property(cn, "clock-frequency", &len);

> -               if (!rate || len != 4) {

> -                       pr_err("%s missing clock-frequency property\n",

> -                               cn->full_name);

> -                       continue;

> -               }

> -

> -               capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;

> -

> -               /* Save min capacity of the system */

> -               if (capacity < min_capacity)

> -                       min_capacity = capacity;

> -

> -               /* Save max capacity of the system */

> -               if (capacity > max_capacity)

> -                       max_capacity = capacity;

> -

> -               cpu_capacity(cpu) = capacity;

>         }

>

> -       /* If min and max capacities are equals, we bypass the update of the

> -        * cpu_scale because all CPUs have the same capacity. Otherwise, we

> -        * compute a middle_capacity factor that will ensure that the capacity

> -        * of an 'average' CPU of the system will be as close as possible to

> -        * SCHED_CAPACITY_SCALE, which is the default value, but with the

> -        * constraint explained near table_efficiency[].

> -        */

> -       if (4*max_capacity < (3*(max_capacity + min_capacity)))

> -               middle_capacity = (min_capacity + max_capacity)

> -                               >> (SCHED_CAPACITY_SHIFT+1);

> -       else

> -               middle_capacity = ((max_capacity / 3)

> -                               >> (SCHED_CAPACITY_SHIFT-1)) + 1;

> -

> -       if (cap_from_dt)

> -               topology_normalize_cpu_scale();


Why have you moved the call to topology_normalize_cpu_scale() from
parse_dt_topology() to update_cpu_capacity() ?

You should keep it in parse_dt_topology() as itis part of the dt
parsing sequence

> -}

> -

> -/*

> - * Look for a customed capacity of a CPU in the cpu_capacity table during the

> - * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the

> - * function returns directly for SMP system.

> - */

> -static void update_cpu_capacity(unsigned int cpu)

> -{

> -       if (!cpu_capacity(cpu) || cap_from_dt)

> -               return;

> -

> -       topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity);

> -

> -       pr_info("CPU%u: update cpu_capacity %lu\n",

> -               cpu, topology_get_cpu_scale(NULL, cpu));

> +       topology_normalize_cpu_scale();

>  }


You can probably just removed update_cpu_capacity()

>

>  #else

>  static inline void parse_dt_topology(void) {}

> -static inline void update_cpu_capacity(unsigned int cpuid) {}

>  #endif

>

>   /*

> @@ -277,8 +172,6 @@ void store_cpu_topology(unsigned int cpuid)

>

>         update_siblings_masks(cpuid);

>

> -       update_cpu_capacity(cpuid);

> -

>         pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",

>                 cpuid, cpu_topology[cpuid].thread_id,

>                 cpu_topology[cpuid].core_id,

> --

> 2.11.0

>

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Dietmar Eggemann Sept. 7, 2017, 10:41 a.m. | #2
On 06/09/17 13:40, Vincent Guittot wrote:
> On 6 September 2017 at 13:43, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:

>> Hi Vincent,

>>

>> On 04/09/17 08:49, Vincent Guittot wrote:

>>> Hi Dietmar,

>>>

>>> Removing cpu effificiency table looks good to me. Nevertheless, i have

>>> some comments below for this patch.

>>

>> Thanks for the review!

>>

>>> On 30 August 2017 at 16:41, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:


[...]

I fixed the issue with the continue statement. Moreover, I think we should also
remove the comment block about 'cpu capacity scale management' and 'cpu capacity
table' on top of  parse_dt_topology() because this is now all handled in
drivers/base/arch_topology.c.

-- >8 --

From: Dietmar Eggemann <dietmar.eggemann@arm.com>

Date: Sun, 9 Jul 2017 23:43:43 +0100
Subject: [PATCH] arm: topology: remove cpu_efficiency

Remove the 'cpu_efficiency/clock-frequency dt property' based solution
to set cpu capacity which was only working for Cortex-A15/A7 arm
big.LITTLE systems.

I.e. the 'capacity-dmips-mhz' based solution is now the only one. It is
shared between arm and arm64 and works for every big.LITTLE system no
matter which core types it consists of.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

---
 arch/arm/kernel/topology.c | 130 ++-------------------------------------------
 1 file changed, 3 insertions(+), 127 deletions(-)

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index bf949a763dbe..5f46d290e34b 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -30,69 +30,11 @@
 #include <asm/cputype.h>
 #include <asm/topology.h>
 
-/*
- * cpu capacity scale management
- */
-
-/*
- * cpu capacity table
- * This per cpu data structure describes the relative capacity of each core.
- * On a heteregenous system, cores don't have the same computation capacity
- * and we reflect that difference in the cpu_capacity field so the scheduler
- * can take this difference into account during load balance. A per cpu
- * structure is preferred because each CPU updates its own cpu_capacity field
- * during the load balance except for idle cores. One idle core is selected
- * to run the rebalance_domains for all idle cores and the cpu_capacity can be
- * updated during this sequence.
- */
-
 #ifdef CONFIG_OF
-struct cpu_efficiency {
-       const char *compatible;
-       unsigned long efficiency;
-};
-
-/*
- * Table of relative efficiency of each processors
- * The efficiency value must fit in 20bit and the final
- * cpu_scale value must be in the range
- *   0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2
- * in order to return at most 1 when DIV_ROUND_CLOSEST
- * is used to compute the capacity of a CPU.
- * Processors that are not defined in the table,
- * use the default SCHED_CAPACITY_SCALE value for cpu_scale.
- */
-static const struct cpu_efficiency table_efficiency[] = {
-       {"arm,cortex-a15", 3891},
-       {"arm,cortex-a7",  2048},
-       {NULL, },
-};
-
-static unsigned long *__cpu_capacity;
-#define cpu_capacity(cpu)      __cpu_capacity[cpu]
-
-static unsigned long middle_capacity = 1;
-static bool cap_from_dt = true;
-
-/*
- * Iterate all CPUs' descriptor in DT and compute the efficiency
- * (as per table_efficiency). Also calculate a middle efficiency
- * as close as possible to  (max{eff_i} - min{eff_i}) / 2
- * This is later used to scale the cpu_capacity field such that an
- * 'average' CPU is of middle capacity. Also see the comments near
- * table_efficiency[] and update_cpu_capacity().
- */
 static void __init parse_dt_topology(void)
 {
-       const struct cpu_efficiency *cpu_eff;
-       struct device_node *cn = NULL;
-       unsigned long min_capacity = ULONG_MAX;
-       unsigned long max_capacity = 0;
-       unsigned long capacity = 0;
-       int cpu = 0;
-
-       __cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),
-                                GFP_NOWAIT);
+       struct device_node *cn;
+       int cpu;
 
        cn = of_find_node_by_path("/cpus");
        if (!cn) {
@@ -101,9 +43,6 @@ static void __init parse_dt_topology(void)
        }
 
        for_each_possible_cpu(cpu) {
-               const u32 *rate;
-               int len;
-
                /* too early to use cpu->of_node */
                cn = of_get_cpu_node(cpu, NULL);
                if (!cn) {
@@ -113,75 +52,14 @@ static void __init parse_dt_topology(void)
 
                if (topology_parse_cpu_capacity(cn, cpu)) {
                        of_node_put(cn);
-                       continue;
                }
-
-               cap_from_dt = false;
-
-               for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
-                       if (of_device_is_compatible(cn, cpu_eff->compatible))
-                               break;
-
-               if (cpu_eff->compatible == NULL)
-                       continue;
-
-               rate = of_get_property(cn, "clock-frequency", &len);
-               if (!rate || len != 4) {
-                       pr_err("%s missing clock-frequency property\n",
-                               cn->full_name);
-                       continue;
-               }
-
-               capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
-
-               /* Save min capacity of the system */
-               if (capacity < min_capacity)
-                       min_capacity = capacity;
-
-               /* Save max capacity of the system */
-               if (capacity > max_capacity)
-                       max_capacity = capacity;
-
-               cpu_capacity(cpu) = capacity;
        }
 
-       /* If min and max capacities are equals, we bypass the update of the
-        * cpu_scale because all CPUs have the same capacity. Otherwise, we
-        * compute a middle_capacity factor that will ensure that the capacity
-        * of an 'average' CPU of the system will be as close as possible to
-        * SCHED_CAPACITY_SCALE, which is the default value, but with the
-        * constraint explained near table_efficiency[].
-        */
-       if (4*max_capacity < (3*(max_capacity + min_capacity)))
-               middle_capacity = (min_capacity + max_capacity)
-                               >> (SCHED_CAPACITY_SHIFT+1);
-       else
-               middle_capacity = ((max_capacity / 3)
-                               >> (SCHED_CAPACITY_SHIFT-1)) + 1;
-
-       if (cap_from_dt)
-               topology_normalize_cpu_scale();
-}
-
-/*
- * Look for a customed capacity of a CPU in the cpu_capacity table during the
- * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
- * function returns directly for SMP system.
- */
-static void update_cpu_capacity(unsigned int cpu)
-{
-       if (!cpu_capacity(cpu) || cap_from_dt)
-               return;
-
-       topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity);
-
-       pr_info("CPU%u: update cpu_capacity %lu\n",
-               cpu, topology_get_cpu_scale(NULL, cpu));
+       topology_normalize_cpu_scale();
 }
 
 #else
 static inline void parse_dt_topology(void) {}
-static inline void update_cpu_capacity(unsigned int cpuid) {}
 #endif
 
  /*
@@ -277,8 +155,6 @@ void store_cpu_topology(unsigned int cpuid)
 
        update_siblings_masks(cpuid);
 
-       update_cpu_capacity(cpuid);
-
        pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
                cpuid, cpu_topology[cpuid].thread_id,
                cpu_topology[cpuid].core_id,
-- 
2.11.0
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Patch

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index bf949a763dbe..04ccfdd94213 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -47,52 +47,10 @@ 
  */
 
 #ifdef CONFIG_OF
-struct cpu_efficiency {
-	const char *compatible;
-	unsigned long efficiency;
-};
-
-/*
- * Table of relative efficiency of each processors
- * The efficiency value must fit in 20bit and the final
- * cpu_scale value must be in the range
- *   0 < cpu_scale < 3*SCHED_CAPACITY_SCALE/2
- * in order to return at most 1 when DIV_ROUND_CLOSEST
- * is used to compute the capacity of a CPU.
- * Processors that are not defined in the table,
- * use the default SCHED_CAPACITY_SCALE value for cpu_scale.
- */
-static const struct cpu_efficiency table_efficiency[] = {
-	{"arm,cortex-a15", 3891},
-	{"arm,cortex-a7",  2048},
-	{NULL, },
-};
-
-static unsigned long *__cpu_capacity;
-#define cpu_capacity(cpu)	__cpu_capacity[cpu]
-
-static unsigned long middle_capacity = 1;
-static bool cap_from_dt = true;
-
-/*
- * Iterate all CPUs' descriptor in DT and compute the efficiency
- * (as per table_efficiency). Also calculate a middle efficiency
- * as close as possible to  (max{eff_i} - min{eff_i}) / 2
- * This is later used to scale the cpu_capacity field such that an
- * 'average' CPU is of middle capacity. Also see the comments near
- * table_efficiency[] and update_cpu_capacity().
- */
 static void __init parse_dt_topology(void)
 {
-	const struct cpu_efficiency *cpu_eff;
-	struct device_node *cn = NULL;
-	unsigned long min_capacity = ULONG_MAX;
-	unsigned long max_capacity = 0;
-	unsigned long capacity = 0;
-	int cpu = 0;
-
-	__cpu_capacity = kcalloc(nr_cpu_ids, sizeof(*__cpu_capacity),
-				 GFP_NOWAIT);
+	struct device_node *cn;
+	int cpu;
 
 	cn = of_find_node_by_path("/cpus");
 	if (!cn) {
@@ -101,9 +59,6 @@  static void __init parse_dt_topology(void)
 	}
 
 	for_each_possible_cpu(cpu) {
-		const u32 *rate;
-		int len;
-
 		/* too early to use cpu->of_node */
 		cn = of_get_cpu_node(cpu, NULL);
 		if (!cn) {
@@ -115,73 +70,13 @@  static void __init parse_dt_topology(void)
 			of_node_put(cn);
 			continue;
 		}
-
-		cap_from_dt = false;
-
-		for (cpu_eff = table_efficiency; cpu_eff->compatible; cpu_eff++)
-			if (of_device_is_compatible(cn, cpu_eff->compatible))
-				break;
-
-		if (cpu_eff->compatible == NULL)
-			continue;
-
-		rate = of_get_property(cn, "clock-frequency", &len);
-		if (!rate || len != 4) {
-			pr_err("%s missing clock-frequency property\n",
-				cn->full_name);
-			continue;
-		}
-
-		capacity = ((be32_to_cpup(rate)) >> 20) * cpu_eff->efficiency;
-
-		/* Save min capacity of the system */
-		if (capacity < min_capacity)
-			min_capacity = capacity;
-
-		/* Save max capacity of the system */
-		if (capacity > max_capacity)
-			max_capacity = capacity;
-
-		cpu_capacity(cpu) = capacity;
 	}
 
-	/* If min and max capacities are equals, we bypass the update of the
-	 * cpu_scale because all CPUs have the same capacity. Otherwise, we
-	 * compute a middle_capacity factor that will ensure that the capacity
-	 * of an 'average' CPU of the system will be as close as possible to
-	 * SCHED_CAPACITY_SCALE, which is the default value, but with the
-	 * constraint explained near table_efficiency[].
-	 */
-	if (4*max_capacity < (3*(max_capacity + min_capacity)))
-		middle_capacity = (min_capacity + max_capacity)
-				>> (SCHED_CAPACITY_SHIFT+1);
-	else
-		middle_capacity = ((max_capacity / 3)
-				>> (SCHED_CAPACITY_SHIFT-1)) + 1;
-
-	if (cap_from_dt)
-		topology_normalize_cpu_scale();
-}
-
-/*
- * Look for a customed capacity of a CPU in the cpu_capacity table during the
- * boot. The update of all CPUs is in O(n^2) for heteregeneous system but the
- * function returns directly for SMP system.
- */
-static void update_cpu_capacity(unsigned int cpu)
-{
-	if (!cpu_capacity(cpu) || cap_from_dt)
-		return;
-
-	topology_set_cpu_scale(cpu, cpu_capacity(cpu) / middle_capacity);
-
-	pr_info("CPU%u: update cpu_capacity %lu\n",
-		cpu, topology_get_cpu_scale(NULL, cpu));
+	topology_normalize_cpu_scale();
 }
 
 #else
 static inline void parse_dt_topology(void) {}
-static inline void update_cpu_capacity(unsigned int cpuid) {}
 #endif
 
  /*
@@ -277,8 +172,6 @@  void store_cpu_topology(unsigned int cpuid)
 
 	update_siblings_masks(cpuid);
 
-	update_cpu_capacity(cpuid);
-
 	pr_info("CPU%u: thread %d, cpu %d, socket %d, mpidr %x\n",
 		cpuid, cpu_topology[cpuid].thread_id,
 		cpu_topology[cpuid].core_id,