Re: [PATCH 06/11] powerpc/smp: Generalize 2nd sched domain
On Mon, Jul 20, 2020 at 11:49:11AM +0530, Srikar Dronamraju wrote:
> * Gautham R Shenoy [2020-07-17 12:07:55]:
>
> > On Tue, Jul 14, 2020 at 10:06:19AM +0530, Srikar Dronamraju wrote:
> > > Currently "CACHE" domain happens to be the 2nd sched domain as per
> > > powerpc_topology. This domain will collapse if cpumask of l2-cache is
> > > same as SMT domain. However we could generalize this domain such that it
> > > could mean either be a "CACHE" domain or a "BIGCORE" domain.
> > >
> > > While setting up the "CACHE" domain, check if shared_cache is already
> > > set.
> > >
> > > Cc: linuxppc-dev
> > > Cc: Michael Ellerman
> > > Cc: Nick Piggin
> > > Cc: Oliver OHalloran
> > > Cc: Nathan Lynch
> > > Cc: Michael Neuling
> > > Cc: Anton Blanchard
> > > Cc: Gautham R Shenoy
> > > Cc: Vaidyanathan Srinivasan
> > > Signed-off-by: Srikar Dronamraju
> > > ---
> > > @@ -867,11 +869,16 @@ static const struct cpumask *smallcore_smt_mask(int
> > > cpu)
> > > }
> > > #endif
> > >
> > > +static const struct cpumask *cpu_bigcore_mask(int cpu)
> > > +{
> > > + return cpu_core_mask(cpu);
> >
> > It should be cpu_smt_mask() if we want the redundant big-core to be
> > degenerated in favour of the SMT level on P8, no? Because
> > cpu_core_mask refers to all the CPUs that are in the same chip.
> >
>
> Right, but it cant be cpu_smt_mask since cpu_smt_mask is only enabled in
> CONFIG_SCHED_SMT. I was looking at using sibling_map, but we have to careful
> for power9 / PowerNV mode. Guess that should be fine.
Ok.
>
> > > +}
> > > +
> > > static struct sched_domain_topology_level powerpc_topology[] = {
> > > #ifdef CONFIG_SCHED_SMT
> > > { cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT) },
> > > #endif
> > > - { shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE) },
> > > + { cpu_bigcore_mask, SD_INIT_NAME(BIGCORE) },
> > > { cpu_cpu_mask, SD_INIT_NAME(DIE) },
> > > { NULL, },
> > > };
> > > @@ -1319,7 +1326,6 @@ static void add_cpu_to_masks(int cpu)
> > > void start_secondary(void *unused)
> > > {
> > > unsigned int cpu = smp_processor_id();
> > > - struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
> > >
> > > mmgrab(_mm);
> > > current->active_mm = _mm;
> > > @@ -1345,14 +1351,20 @@ void start_secondary(void *unused)
> > > /* Update topology CPU masks */
> > > add_cpu_to_masks(cpu);
> > >
> > > - if (has_big_cores)
> > > - sibling_mask = cpu_smallcore_mask;
> > > /*
> > >* Check for any shared caches. Note that this must be done on a
> > >* per-core basis because one core in the pair might be disabled.
> > >*/
> > > - if (!cpumask_equal(cpu_l2_cache_mask(cpu), sibling_mask(cpu)))
> > > - shared_caches = true;
> > > + if (!shared_caches) {
> > > + struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
> > > + struct cpumask *mask = cpu_l2_cache_mask(cpu);
> > > +
> > > + if (has_big_cores)
> > > + sibling_mask = cpu_smallcore_mask;
> > > +
> > > + if (cpumask_weight(mask) > cpumask_weight(sibling_mask(cpu)))
> > > + shared_caches = true;
> >
> > Shouldn't we use cpumask_subset() here ?
>
> Wouldn't cpumask_subset should return 1 if both are same?
When are caches shared ? When the sibling_mask(cpu) is a
strict-subset of cpu_l2_cache_mask(cpu). cpumask_weight() only
checks if the number of CPUs in cpu_l2_cache_mask(cpu) is greater than
sibling_mask(cpu) but not if constituent CPUs of the former forms
a strict superset of the latter.
We are better off using
if (!cpumask_equal(sibling_mask(cpu), mask) &&
cpumask_subset(sibling_mask(cpu), mask))
which is accurate.
> We dont want to have shared_caches set if both the masks are equal.
>
> >
> > > + }
> > >
> > > set_numa_node(numa_cpu_lookup_table[cpu]);
> > > set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
> > > @@ -1390,6 +1402,14 @@ void __init smp_cpus_done(unsigned int max_cpus)
> > > smp_ops->bringup_done();
> > >
> > > dump_numa_cpu_topology();
> > > + if (shared_caches) {
> > > + pr_info("Using shared cache scheduler topology\n");
> > > + powerpc_topology[bigcore_idx].mask = shared_cache_mask;
> > > +#ifdef CONFIG_SCHED_DEBUG
> > > + powerpc_topology[bigcore_idx].name = "CACHE";
> > > +#endif
> > > + powerpc_topology[bigcore_idx].sd_flags =
> > > powerpc_shared_cache_flags;
> > > + }
> >
> >
> > I would much rather that we have all the topology-fixups done in one
> > function.
> >
> > fixup_topology(void) {
> > if (has_big_core)
> > powerpc_topology[smt_idx].mask = smallcore_smt_mask;
> >
> > if (shared_caches) {
> >const char *name = "CACHE";
> >powerpc_topology[bigcore_idx].mask = shared_cache_mask;
> >strlcpy(powerpc_topology[bigcore_idx].name, name,
> > strlen(name));
> >powerpc_topology[bigcore_idx].sd_flags =
Re: [PATCH 06/11] powerpc/smp: Generalize 2nd sched domain
* Gautham R Shenoy [2020-07-17 12:07:55]:
> On Tue, Jul 14, 2020 at 10:06:19AM +0530, Srikar Dronamraju wrote:
> > Currently "CACHE" domain happens to be the 2nd sched domain as per
> > powerpc_topology. This domain will collapse if cpumask of l2-cache is
> > same as SMT domain. However we could generalize this domain such that it
> > could mean either be a "CACHE" domain or a "BIGCORE" domain.
> >
> > While setting up the "CACHE" domain, check if shared_cache is already
> > set.
> >
> > Cc: linuxppc-dev
> > Cc: Michael Ellerman
> > Cc: Nick Piggin
> > Cc: Oliver OHalloran
> > Cc: Nathan Lynch
> > Cc: Michael Neuling
> > Cc: Anton Blanchard
> > Cc: Gautham R Shenoy
> > Cc: Vaidyanathan Srinivasan
> > Signed-off-by: Srikar Dronamraju
> > ---
> > @@ -867,11 +869,16 @@ static const struct cpumask *smallcore_smt_mask(int
> > cpu)
> > }
> > #endif
> >
> > +static const struct cpumask *cpu_bigcore_mask(int cpu)
> > +{
> > + return cpu_core_mask(cpu);
>
> It should be cpu_smt_mask() if we want the redundant big-core to be
> degenerated in favour of the SMT level on P8, no? Because
> cpu_core_mask refers to all the CPUs that are in the same chip.
>
Right, but it cant be cpu_smt_mask since cpu_smt_mask is only enabled in
CONFIG_SCHED_SMT. I was looking at using sibling_map, but we have to careful
for power9 / PowerNV mode. Guess that should be fine.
> > +}
> > +
> > static struct sched_domain_topology_level powerpc_topology[] = {
> > #ifdef CONFIG_SCHED_SMT
> > { cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT) },
> > #endif
> > - { shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE) },
> > + { cpu_bigcore_mask, SD_INIT_NAME(BIGCORE) },
> > { cpu_cpu_mask, SD_INIT_NAME(DIE) },
> > { NULL, },
> > };
> > @@ -1319,7 +1326,6 @@ static void add_cpu_to_masks(int cpu)
> > void start_secondary(void *unused)
> > {
> > unsigned int cpu = smp_processor_id();
> > - struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
> >
> > mmgrab(_mm);
> > current->active_mm = _mm;
> > @@ -1345,14 +1351,20 @@ void start_secondary(void *unused)
> > /* Update topology CPU masks */
> > add_cpu_to_masks(cpu);
> >
> > - if (has_big_cores)
> > - sibling_mask = cpu_smallcore_mask;
> > /*
> > * Check for any shared caches. Note that this must be done on a
> > * per-core basis because one core in the pair might be disabled.
> > */
> > - if (!cpumask_equal(cpu_l2_cache_mask(cpu), sibling_mask(cpu)))
> > - shared_caches = true;
> > + if (!shared_caches) {
> > + struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
> > + struct cpumask *mask = cpu_l2_cache_mask(cpu);
> > +
> > + if (has_big_cores)
> > + sibling_mask = cpu_smallcore_mask;
> > +
> > + if (cpumask_weight(mask) > cpumask_weight(sibling_mask(cpu)))
> > + shared_caches = true;
>
> Shouldn't we use cpumask_subset() here ?
Wouldn't cpumask_subset should return 1 if both are same?
We dont want to have shared_caches set if both the masks are equal.
>
> > + }
> >
> > set_numa_node(numa_cpu_lookup_table[cpu]);
> > set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
> > @@ -1390,6 +1402,14 @@ void __init smp_cpus_done(unsigned int max_cpus)
> > smp_ops->bringup_done();
> >
> > dump_numa_cpu_topology();
> > + if (shared_caches) {
> > + pr_info("Using shared cache scheduler topology\n");
> > + powerpc_topology[bigcore_idx].mask = shared_cache_mask;
> > +#ifdef CONFIG_SCHED_DEBUG
> > + powerpc_topology[bigcore_idx].name = "CACHE";
> > +#endif
> > + powerpc_topology[bigcore_idx].sd_flags =
> > powerpc_shared_cache_flags;
> > + }
>
>
> I would much rather that we have all the topology-fixups done in one
> function.
>
> fixup_topology(void) {
> if (has_big_core)
> powerpc_topology[smt_idx].mask = smallcore_smt_mask;
>
> if (shared_caches) {
>const char *name = "CACHE";
>powerpc_topology[bigcore_idx].mask = shared_cache_mask;
>strlcpy(powerpc_topology[bigcore_idx].name, name,
> strlen(name));
>powerpc_topology[bigcore_idx].sd_flags = powerpc_shared_cache_flags;
> }
>
> /* Any other changes to the topology structure here */
We could do this.
>
> And also as an optimization, get rid of degenerate structures here
> itself so that we don't pay additional penalty while building the
> sched-domains each time.
>
Yes this is definitely in plan, but slightly later in time.
Thanks for the review and comments.
--
Thanks and Regards
Srikar Dronamraju
Re: [PATCH 06/11] powerpc/smp: Generalize 2nd sched domain
On Tue, Jul 14, 2020 at 10:06:19AM +0530, Srikar Dronamraju wrote:
> Currently "CACHE" domain happens to be the 2nd sched domain as per
> powerpc_topology. This domain will collapse if cpumask of l2-cache is
> same as SMT domain. However we could generalize this domain such that it
> could mean either be a "CACHE" domain or a "BIGCORE" domain.
>
> While setting up the "CACHE" domain, check if shared_cache is already
> set.
>
> Cc: linuxppc-dev
> Cc: Michael Ellerman
> Cc: Nick Piggin
> Cc: Oliver OHalloran
> Cc: Nathan Lynch
> Cc: Michael Neuling
> Cc: Anton Blanchard
> Cc: Gautham R Shenoy
> Cc: Vaidyanathan Srinivasan
> Signed-off-by: Srikar Dronamraju
> ---
> arch/powerpc/kernel/smp.c | 48 +++
> 1 file changed, 34 insertions(+), 14 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 875f57e41355..f8faf75135af 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -85,6 +85,14 @@ EXPORT_PER_CPU_SYMBOL(cpu_l2_cache_map);
> EXPORT_PER_CPU_SYMBOL(cpu_core_map);
> EXPORT_SYMBOL_GPL(has_big_cores);
>
> +enum {
> +#ifdef CONFIG_SCHED_SMT
> + smt_idx,
> +#endif
> + bigcore_idx,
> + die_idx,
> +};
> +
> #define MAX_THREAD_LIST_SIZE 8
> #define THREAD_GROUP_SHARE_L1 1
> struct thread_groups {
> @@ -851,13 +859,7 @@ static int powerpc_shared_cache_flags(void)
> */
> static const struct cpumask *shared_cache_mask(int cpu)
> {
> - if (shared_caches)
> - return cpu_l2_cache_mask(cpu);
> -
> - if (has_big_cores)
> - return cpu_smallcore_mask(cpu);
> -
> - return cpu_smt_mask(cpu);
> + return per_cpu(cpu_l2_cache_map, cpu);
> }
>
> #ifdef CONFIG_SCHED_SMT
> @@ -867,11 +869,16 @@ static const struct cpumask *smallcore_smt_mask(int cpu)
> }
> #endif
>
> +static const struct cpumask *cpu_bigcore_mask(int cpu)
> +{
> + return cpu_core_mask(cpu);
It should be cpu_smt_mask() if we want the redundant big-core to be
degenerated in favour of the SMT level on P8, no? Because
cpu_core_mask refers to all the CPUs that are in the same chip.
> +}
> +
> static struct sched_domain_topology_level powerpc_topology[] = {
> #ifdef CONFIG_SCHED_SMT
> { cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT) },
> #endif
> - { shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE) },
> + { cpu_bigcore_mask, SD_INIT_NAME(BIGCORE) },
> { cpu_cpu_mask, SD_INIT_NAME(DIE) },
> { NULL, },
> };
> @@ -895,7 +902,7 @@ static int init_big_cores(void)
>
> #ifdef CONFIG_SCHED_SMT
> pr_info("Big cores detected. Using small core scheduling\n");
> - powerpc_topology[0].mask = smallcore_smt_mask;
> + powerpc_topology[smt_idx].mask = smallcore_smt_mask;
> #endif
>
> return 0;
> @@ -1319,7 +1326,6 @@ static void add_cpu_to_masks(int cpu)
> void start_secondary(void *unused)
> {
> unsigned int cpu = smp_processor_id();
> - struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
>
> mmgrab(_mm);
> current->active_mm = _mm;
> @@ -1345,14 +1351,20 @@ void start_secondary(void *unused)
> /* Update topology CPU masks */
> add_cpu_to_masks(cpu);
>
> - if (has_big_cores)
> - sibling_mask = cpu_smallcore_mask;
> /*
>* Check for any shared caches. Note that this must be done on a
>* per-core basis because one core in the pair might be disabled.
>*/
> - if (!cpumask_equal(cpu_l2_cache_mask(cpu), sibling_mask(cpu)))
> - shared_caches = true;
> + if (!shared_caches) {
> + struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
> + struct cpumask *mask = cpu_l2_cache_mask(cpu);
> +
> + if (has_big_cores)
> + sibling_mask = cpu_smallcore_mask;
> +
> + if (cpumask_weight(mask) > cpumask_weight(sibling_mask(cpu)))
> + shared_caches = true;
Shouldn't we use cpumask_subset() here ?
> + }
>
> set_numa_node(numa_cpu_lookup_table[cpu]);
> set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
> @@ -1390,6 +1402,14 @@ void __init smp_cpus_done(unsigned int max_cpus)
> smp_ops->bringup_done();
>
> dump_numa_cpu_topology();
> + if (shared_caches) {
> + pr_info("Using shared cache scheduler topology\n");
> + powerpc_topology[bigcore_idx].mask = shared_cache_mask;
> +#ifdef CONFIG_SCHED_DEBUG
> + powerpc_topology[bigcore_idx].name = "CACHE";
> +#endif
> + powerpc_topology[bigcore_idx].sd_flags =
> powerpc_shared_cache_flags;
> + }
I would much rather that we have all the topology-fixups done in one
function.
fixup_topology(void) {
if (has_big_core)
powerpc_topology[smt_idx].mask = smallcore_smt_mask;
if (shared_caches) {
const char *name = "CACHE";
powerpc_topology[bigcore_idx].mask =
[PATCH 06/11] powerpc/smp: Generalize 2nd sched domain
Currently "CACHE" domain happens to be the 2nd sched domain as per
powerpc_topology. This domain will collapse if cpumask of l2-cache is
same as SMT domain. However we could generalize this domain such that it
could mean either be a "CACHE" domain or a "BIGCORE" domain.
While setting up the "CACHE" domain, check if shared_cache is already
set.
Cc: linuxppc-dev
Cc: Michael Ellerman
Cc: Nick Piggin
Cc: Oliver OHalloran
Cc: Nathan Lynch
Cc: Michael Neuling
Cc: Anton Blanchard
Cc: Gautham R Shenoy
Cc: Vaidyanathan Srinivasan
Signed-off-by: Srikar Dronamraju
---
arch/powerpc/kernel/smp.c | 48 +++
1 file changed, 34 insertions(+), 14 deletions(-)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 875f57e41355..f8faf75135af 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -85,6 +85,14 @@ EXPORT_PER_CPU_SYMBOL(cpu_l2_cache_map);
EXPORT_PER_CPU_SYMBOL(cpu_core_map);
EXPORT_SYMBOL_GPL(has_big_cores);
+enum {
+#ifdef CONFIG_SCHED_SMT
+ smt_idx,
+#endif
+ bigcore_idx,
+ die_idx,
+};
+
#define MAX_THREAD_LIST_SIZE 8
#define THREAD_GROUP_SHARE_L1 1
struct thread_groups {
@@ -851,13 +859,7 @@ static int powerpc_shared_cache_flags(void)
*/
static const struct cpumask *shared_cache_mask(int cpu)
{
- if (shared_caches)
- return cpu_l2_cache_mask(cpu);
-
- if (has_big_cores)
- return cpu_smallcore_mask(cpu);
-
- return cpu_smt_mask(cpu);
+ return per_cpu(cpu_l2_cache_map, cpu);
}
#ifdef CONFIG_SCHED_SMT
@@ -867,11 +869,16 @@ static const struct cpumask *smallcore_smt_mask(int cpu)
}
#endif
+static const struct cpumask *cpu_bigcore_mask(int cpu)
+{
+ return cpu_core_mask(cpu);
+}
+
static struct sched_domain_topology_level powerpc_topology[] = {
#ifdef CONFIG_SCHED_SMT
{ cpu_smt_mask, powerpc_smt_flags, SD_INIT_NAME(SMT) },
#endif
- { shared_cache_mask, powerpc_shared_cache_flags, SD_INIT_NAME(CACHE) },
+ { cpu_bigcore_mask, SD_INIT_NAME(BIGCORE) },
{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
{ NULL, },
};
@@ -895,7 +902,7 @@ static int init_big_cores(void)
#ifdef CONFIG_SCHED_SMT
pr_info("Big cores detected. Using small core scheduling\n");
- powerpc_topology[0].mask = smallcore_smt_mask;
+ powerpc_topology[smt_idx].mask = smallcore_smt_mask;
#endif
return 0;
@@ -1319,7 +1326,6 @@ static void add_cpu_to_masks(int cpu)
void start_secondary(void *unused)
{
unsigned int cpu = smp_processor_id();
- struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
mmgrab(_mm);
current->active_mm = _mm;
@@ -1345,14 +1351,20 @@ void start_secondary(void *unused)
/* Update topology CPU masks */
add_cpu_to_masks(cpu);
- if (has_big_cores)
- sibling_mask = cpu_smallcore_mask;
/*
* Check for any shared caches. Note that this must be done on a
* per-core basis because one core in the pair might be disabled.
*/
- if (!cpumask_equal(cpu_l2_cache_mask(cpu), sibling_mask(cpu)))
- shared_caches = true;
+ if (!shared_caches) {
+ struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
+ struct cpumask *mask = cpu_l2_cache_mask(cpu);
+
+ if (has_big_cores)
+ sibling_mask = cpu_smallcore_mask;
+
+ if (cpumask_weight(mask) > cpumask_weight(sibling_mask(cpu)))
+ shared_caches = true;
+ }
set_numa_node(numa_cpu_lookup_table[cpu]);
set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
@@ -1390,6 +1402,14 @@ void __init smp_cpus_done(unsigned int max_cpus)
smp_ops->bringup_done();
dump_numa_cpu_topology();
+ if (shared_caches) {
+ pr_info("Using shared cache scheduler topology\n");
+ powerpc_topology[bigcore_idx].mask = shared_cache_mask;
+#ifdef CONFIG_SCHED_DEBUG
+ powerpc_topology[bigcore_idx].name = "CACHE";
+#endif
+ powerpc_topology[bigcore_idx].sd_flags =
powerpc_shared_cache_flags;
+ }
set_sched_topology(powerpc_topology);
}
--
2.17.1
