github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-12 16:18:45 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity

sched/fair: Avoid rq->lock bouncing in sched_balance_newidle()

Browse Source 
While poking at this code recently I noted we do a pointless
unlock+lock cycle in sched_balance_newidle(). We drop the rq->lock (so
we can balance) but then instantly grab the same rq->lock again in
sched_balance_update_blocked_averages().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251127154725.532469061@infradead.org
This commit is contained in:
Peter Zijlstra 2025-11-12 16:08:23 +01:00 committed by Ingo Molnar
parent 089d84203a
commit 45e0922508
1 changed files with 18 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
kernel/sched/fair.c
View File

@ -9905,15 +9905,11 @@ static unsigned long task_h_load(struct task_struct *p)
}
#endif /* !CONFIG_FAIR_GROUP_SCHED */
static void sched_balance_update_blocked_averages(int cpu)
static void __sched_balance_update_blocked_averages(struct rq *rq)
{
bool decayed = false, done = true;
struct rq *rq = cpu_rq(cpu);
struct rq_flags rf;
rq_lock_irqsave(rq, &rf);
update_blocked_load_tick(rq);
update_rq_clock(rq);
decayed |= __update_blocked_others(rq, &done);
decayed |= __update_blocked_fair(rq, &done);
@ -9921,7 +9917,15 @@ static void sched_balance_update_blocked_averages(int cpu)
update_blocked_load_status(rq, !done);
if (decayed)
cpufreq_update_util(rq, 0);
rq_unlock_irqrestore(rq, &rf);
}
static void sched_balance_update_blocked_averages(int cpu)
{
struct rq *rq = cpu_rq(cpu);
guard(rq_lock_irqsave)(rq);
update_rq_clock(rq);
__sched_balance_update_blocked_averages(rq);
}
/********** Helpers for sched_balance_find_src_group ************************/
@ -12868,12 +12872,17 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf)
}
rcu_read_unlock();
/*
* Include sched_balance_update_blocked_averages() in the cost
* calculation because it can be quite costly -- this ensures we skip
* it when avg_idle gets to be very low.
*/
t0 = sched_clock_cpu(this_cpu);
__sched_balance_update_blocked_averages(this_rq);
rq_modified_clear(this_rq);
raw_spin_rq_unlock(this_rq);
t0 = sched_clock_cpu(this_cpu);
sched_balance_update_blocked_averages(this_cpu);
rcu_read_lock();
for_each_domain(this_cpu, sd) {
u64 domain_cost;