* Ingo Molnar <mi...@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();
--
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