On Thu, Dec 19, 2019 at 09:59:48AM +0800, Ming Lei wrote:

quoted

So pray tell, why did you not integrate this with IRQ_TIME_ACCOUNTING ?
That already takes a timestamp and does most of what you need.

Yeah, that was the 1st approach I thought of, but IRQ_TIME_ACCOUNTING
may be disabled, and enabling it may cause observable effect on IO
performance.

Is that an actual concern, are people disabling it?

quoted

quoted

@@ -356,6 +512,7 @@ void irq_enter(void)
 	}
 
 	__irq_enter();
+	irq_interval_update();
 }

Arggh.. you're going to make every single interrupt take at least 2
extra cache misses for this gunk?!?

Could you explain it a bit why two cache misses are involved?

I understand at most one miss is caused, which should only happen in
irq_interval_update(), and what is the other one?

The rq clock thing IIRC.