(fixed the subject to include the patch title. Patch quoted below.)

* Ingo Molnar mingo@kernel.org wrote:

• Ingo Molnar mingo@kernel.org wrote:

...

This would speed up various hrtimer primitives like hrtimer_remove()/add and simplify the code. It would be a net code shrink as well.

Totally untested patch below. It gives:

text data bss dec hex filename 7502 427 0 7929 1ef9 hrtimer.o.before 7422 427 0 7849 1ea9 hrtimer.o.after

and half of that code removal is from hot paths.

This would simplify the followup step of skipping over inactive bases as well.

The followup step is attached below (untested as well).

Note that all other iterations already had a check for active.next, so the patch doesn't even bloat anything:

text data bss dec hex filename 7422 427 0 7849 1ea9 hrtimer.o.before 7422 427 0 7849 1ea9 hrtimer.o.after

(I did a rename within migrate_hrtimers() because it used 'cpu_base' vs 'clock_base' inconsistently in a confusing (to me) manner.)

I'd also suggest the removal of the timerqueue_getnext() obfuscation: it 'sounds' complex but in reality it's a simple dereference to active.next. I think this is what triggered this rather pointless maintenance of active_bases.

Thanks,

Ingo

---

kernel/time/hrtimer.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-)

Index: tip/kernel/time/hrtimer.c

--- tip.orig/kernel/time/hrtimer.c +++ tip/kernel/time/hrtimer.c @@ -1660,29 +1660,35 @@ static void migrate_hrtimer_list(struct static void migrate_hrtimers(int scpu) {

• struct hrtimer_cpu_base *old_base, *new_base;

• struct hrtimer_cpu_base *old_cpu_base, *new_cpu_base; int i;

BUG_ON(cpu_online(scpu)); tick_cancel_sched_timer(scpu); local_irq_disable();

• old_base = &per_cpu(hrtimer_bases, scpu);
• new_base = this_cpu_ptr(&hrtimer_bases);

• old_cpu_base = &per_cpu(hrtimer_bases, scpu);
• new_cpu_base = this_cpu_ptr(&hrtimer_bases); /*
  • The caller is globally serialized and nobody else
  • takes two locks at once, deadlock is not possible.
  */

• raw_spin_lock(&new_base->lock);
• raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

• raw_spin_lock(&new_cpu_base->lock);
• raw_spin_lock_nested(&old_cpu_base->lock, SINGLE_DEPTH_NESTING);

for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {

• migrate_hrtimer_list(&old_base->clock_base[i],
  

• 		     &new_base->clock_base[i]);
  

• struct hrtimer_clock_base *old_base = old_cpu_base->clock_base + i;
  

• struct hrtimer_clock_base *new_base;
  

• if (!old_base->active.next)
  

• 	continue;
  

• new_base = new_cpu_base->clock_base + i;
  

• migrate_hrtimer_list(old_base, new_base);
  

  }

• raw_spin_unlock(&old_base->lock);
• raw_spin_unlock(&new_base->lock);

• raw_spin_unlock(&old_cpu_base->lock);
• raw_spin_unlock(&new_cpu_base->lock);

/* Check, if we got expired work to do */ __hrtimer_peek_ahead_timers();