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sched/fair: Get this cpu once in find_new_ilb()

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Calling smp_processor_id() on:
 - In CONFIG_DEBUG_PREEMPT=y, if preemption/irq is disabled, then it does
   not print any warning.
 - In CONFIG_DEBUG_PREEMPT=n, it doesn't do anything apart from getting
   __smp_processor_id

So with both CONFIG_DEBUG_PREEMPT=y/n, in preemption disabled section
it is better to cache the value. It could save a few cycles. Though
tiny, repeated in loop could add up to a small value.

find_new_ilb is called in interrupt context. So preemption is disabled.
So Hoist the this_cpu out of loop

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260323193630.640311-2-sshegde@linux.ibm.com
This commit is contained in:
Shrikanth Hegde 2026-03-24 01:06:27 +05:30 committed by Peter Zijlstra
parent e379dce8af
commit 76504bce4e
1 changed files with 2 additions and 2 deletions
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4
kernel/sched/fair.c
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@ -12614,14 +12614,14 @@ static inline int on_null_domain(struct rq *rq)
*/
static inline int find_new_ilb(void)
{
int this_cpu = smp_processor_id();
const struct cpumask *hk_mask;
int ilb_cpu;
hk_mask = housekeeping_cpumask(HK_TYPE_KERNEL_NOISE);
for_each_cpu_and(ilb_cpu, nohz.idle_cpus_mask, hk_mask) {
if (ilb_cpu == smp_processor_id())
if (ilb_cpu == this_cpu)
continue;
if (idle_cpu(ilb_cpu))