[dovetail][RFC PATCH 3/5] kernel/irq/pipeline: Instrument irq_post_stage and pull_next_irq

[Florian Bezdeka via Xenomai]

 - Remember how often an IRQ was posted into and pulled from the IRQ log
 - Measure the time between push and pull
 - Count how often we merge IRQs
   (multiple post events before pulling again)

Signed-off-by: Florian Bezdeka <florian.bezd...@siemens.com>
---
 kernel/irq/pipeline.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/kernel/irq/pipeline.c b/kernel/irq/pipeline.c
index f64d731e8db1..7fcc03b74459 100644
--- a/kernel/irq/pipeline.c
+++ b/kernel/irq/pipeline.c
@@ -592,10 +592,18 @@ static inline bool irq_post_check(struct irq_stage 
*stage, unsigned int irq)
 
 #if __IRQ_STAGE_MAP_LEVELS == 4
 
+static inline struct pipe_stats __percpu *get_stage_stats(struct irq_stage *s,
+                                                         struct irq_desc *desc)
+{
+       return this_cpu_ptr(s->index == 0 ? desc->ib_stats : desc->oob_stats);
+}
+
 /* Must be called hard irqs off. */
 void irq_post_stage(struct irq_stage *stage, unsigned int irq)
 {
        struct irq_stage_data *p = this_staged(stage);
+       struct irq_desc *desc = irq_to_cached_desc(irq);
+       struct pipe_stats __percpu *stats = get_stage_stats(stage, desc);
        int l0b, l1b, l2b;
 
        if (irq_post_check(stage, irq))
@@ -605,10 +613,20 @@ void irq_post_stage(struct irq_stage *stage, unsigned int 
irq)
        l1b = irq / (BITS_PER_LONG * BITS_PER_LONG);
        l2b = irq / BITS_PER_LONG;
 
+       if (test_bit(irq, p->log.map->flat)
+           && test_bit(l2b, p->log.map->index_2)
+           && test_bit(l1b, p->log.map->index_1)
+           && test_bit(l0b, &p->log.index_0))
+               stats->post_merge_cnt++;
+       else
+               stats->post_time = local_clock();
+
        __set_bit(irq, p->log.map->flat);
        __set_bit(l2b, p->log.map->index_2);
        __set_bit(l1b, p->log.map->index_1);
        __set_bit(l0b, &p->log.index_0);
+
+       stats->post_cnt++;
 }
 EXPORT_SYMBOL_GPL(irq_post_stage);
 
@@ -619,6 +637,9 @@ EXPORT_SYMBOL_GPL(irq_post_stage);
 static inline int pull_next_irq(struct irq_stage_data *p)
 {
        unsigned long l0m, l1m, l2m, l3m;
+       struct irq_desc *desc;
+       struct pipe_stats __percpu *stats;
+       u64 core_time, max_log_time, diff;
        int l0b, l1b, l2b, l3b;
        unsigned int irq;
 
@@ -660,6 +681,19 @@ static inline int pull_next_irq(struct irq_stage_data *p)
                }
        }
 
+       desc = irq_to_cached_desc(irq);
+       stats = get_stage_stats(p->stage, desc);
+
+       core_time = local_clock();
+       stats->pull_time = core_time;
+       stats->pull_cnt++;
+
+       max_log_time = stats->max_log_time;
+       diff = core_time - stats->post_time;
+
+       if (diff > max_log_time)
+               stats->max_log_time = diff;
+
        return irq;
 }
 
-- 
2.30.2