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SubjectRe: Affinity managed interrupts vs non-managed interrupts
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Hi Thomas, Kashyap,

At 09/04/2018 06:29 PM, Kashyap Desai wrote:
>>> I am using " for-4.19/block " and this particular patch "a0c9259
>>> irq/matrix: Spread interrupts on allocation" is included.
>>

IMO, this patch is just used for non-managed interrupts.

>> So if all 16 have their effective affinity set to CPU0 then that's
> strange

But, all these 16 are managed interrupts, and will be assigned vectors
by assign_managed_vector():
{
cpumask_and(vector_searchmask, vector_searchmask, affmsk);
cpu = cpumask_first(vector_searchmask);

...
vector = irq_matrix_alloc_managed(vector_matrix, cpu);
...
}

Where we always used the *first* cpu in the vector_searchmask(0-71), not
the suitable one. So I guess this situation happened.

Shall we also spread the managed interrupts on allocation?

Thanks,
dou
-----------------8<----------------------------------------

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 9f148e3d45b4..57dc05691f44 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -314,13 +314,12 @@ assign_managed_vector(struct irq_data *irqd, const
struct cpumask *dest)
int vector, cpu;

cpumask_and(vector_searchmask, vector_searchmask, affmsk);
- cpu = cpumask_first(vector_searchmask);
- if (cpu >= nr_cpu_ids)
- return -EINVAL;
+
/* set_affinity might call here for nothing */
if (apicd->vector && cpumask_test_cpu(apicd->cpu,
vector_searchmask))
return 0;
- vector = irq_matrix_alloc_managed(vector_matrix, cpu);
+
+ vector = irq_matrix_alloc_managed(vector_matrix,
vector_searchmask, &cpu);
trace_vector_alloc_managed(irqd->irq, vector, vector);
if (vector < 0)
return vector;
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 201de12a9957..36fdeff5043a 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -1151,7 +1151,8 @@ void irq_matrix_offline(struct irq_matrix *m);
void irq_matrix_assign_system(struct irq_matrix *m, unsigned int bit,
bool replace);
int irq_matrix_reserve_managed(struct irq_matrix *m, const struct
cpumask *msk);
void irq_matrix_remove_managed(struct irq_matrix *m, const struct
cpumask *msk);
-int irq_matrix_alloc_managed(struct irq_matrix *m, unsigned int cpu);
+int irq_matrix_alloc_managed(struct irq_matrix *m, const struct cpumask
*msk,
+ unsigned int *mapped_cpu);
void irq_matrix_reserve(struct irq_matrix *m);
void irq_matrix_remove_reserved(struct irq_matrix *m);
int irq_matrix_alloc(struct irq_matrix *m, const struct cpumask *msk,
diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index 5092494bf261..d9e4e0a385fa 100644
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -239,21 +239,40 @@ void irq_matrix_remove_managed(struct irq_matrix
*m, const struct cpumask *msk)
* @m: Matrix pointer
* @cpu: On which CPU the interrupt should be allocated
*/
-int irq_matrix_alloc_managed(struct irq_matrix *m, unsigned int cpu)
+int irq_matrix_alloc_managed(struct irq_matrix *m, const struct cpumask
*msk,
+ unsigned int *mapped_cpu)
{
- struct cpumap *cm = per_cpu_ptr(m->maps, cpu);
- unsigned int bit, end = m->alloc_end;
-
- /* Get managed bit which are not allocated */
- bitmap_andnot(m->scratch_map, cm->managed_map, cm->alloc_map, end);
- bit = find_first_bit(m->scratch_map, end);
- if (bit >= end)
- return -ENOSPC;
- set_bit(bit, cm->alloc_map);
- cm->allocated++;
- m->total_allocated++;
- trace_irq_matrix_alloc_managed(bit, cpu, m, cm);
- return bit;
+ unsigned int cpu, best_cpu, maxavl = 0;
+ unsigned int bit, end;
+ struct cpumap *cm;
+
+ best_cpu = UINT_MAX;
+ for_each_cpu(cpu, msk) {
+ cm = per_cpu_ptr(m->maps, cpu);
+
+ if (!cm->online || cm->available <= maxavl)
+ continue;
+
+ best_cpu = cpu;
+ maxavl = cm->available;
+ }
+
+ if (maxavl) {
+ cm = per_cpu_ptr(m->maps, best_cpu);
+ end = m->alloc_end;
+ /* Get managed bit which are not allocated */
+ bitmap_andnot(m->scratch_map, cm->managed_map,
cm->alloc_map, end);
+ bit = find_first_bit(m->scratch_map, end);
+ if (bit >= end)
+ return -ENOSPC;
+ set_bit(bit, cm->alloc_map);
+ cm->allocated++;
+ m->total_allocated++;
+ *mapped_cpu = best_cpu;
+ trace_irq_matrix_alloc_managed(bit, cpu, m, cm);
+ return bit;
+ }
+ return -ENOSPC;
}

/**
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