Optimize the timer interrupt function to avoid timer_interrupt
delayed/SLOW messages:
- always do the "cheap" math, it's much faster.
- avoid calling mtctl() twice if we want to skip one clocktick
- do the house keeping (update counters) before we printk() some
warnings
Overall those changes reduced the amount of timer_interrupt kernel
warnings a lot for me.
Signed-off-by: Helge Deller <deller@xxxxxx>
diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
index 70e105d..5a16c12 100644
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -77,7 +77,7 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
cycles_elapsed = now - next_tick;
- if ((cycles_elapsed >> 6) < cpt) {
+ if (1 || (cycles_elapsed >> 6) < cpt) {
/* use "cheap" math (add/subtract) instead
* of the more expensive div/mul method
*/
@@ -105,10 +105,8 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
/* Program the IT when to deliver the next interrupt.
* Only bottom 32-bits of next_tick are writable in CR16!
- */
- mtctl(next_tick, 16);
-
- /* Skip one clocktick on purpose if we missed next_tick.
+ *
+ * Skip one clocktick on purpose if we missed next_tick.
* The new CR16 must be "later" than current CR16 otherwise
* itimer would not fire until CR16 wrapped - e.g 4 seconds
* later on a 1Ghz processor. We'll account for the missed
@@ -121,6 +119,20 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
now2 = mfctl(16);
if (next_tick - now2 > cpt)
mtctl(next_tick+cpt, 16);
+ else
+ mtctl(next_tick, 16);
+
+ /* Done mucking with unreliable delivery of interrupts.
+ * Go do system house keeping.
+ */
+
+ if (!--cpuinfo->prof_counter) {
+ cpuinfo->prof_counter = cpuinfo->prof_multiplier;
+ update_process_times(user_mode(get_irq_regs()));
+ }
+
+ if (cpu == 0)
+ xtime_update(ticks_elapsed);
#if 1
/*
@@ -154,18 +166,6 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
next_tick, now );
}
- /* Done mucking with unreliable delivery of interrupts.
- * Go do system house keeping.
- */
-
- if (!--cpuinfo->prof_counter) {
- cpuinfo->prof_counter = cpuinfo->prof_multiplier;
- update_process_times(user_mode(get_irq_regs()));
- }
-
- if (cpu == 0)
- xtime_update(ticks_elapsed);
-
return IRQ_HANDLED;
}
--
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