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| author | Valentin Schneider <valentin.schneider@arm.com> | 2021-08-23 12:16:59 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-05 15:51:30 +0200 |
| commit | efd984c481abb516fab8bafb25bf41fd9397a43c (patch) | |
| tree | 456c643db81f5548a2d0395a234f5c5aee789db9 /kernel/sched/fair.c | |
| parent | 9e1ff307c779ce1f0f810c7ecce3d95bbae40896 (diff) | |
| download | linux-stable-efd984c481abb516fab8bafb25bf41fd9397a43c.tar.gz linux-stable-efd984c481abb516fab8bafb25bf41fd9397a43c.tar.bz2 linux-stable-efd984c481abb516fab8bafb25bf41fd9397a43c.zip | |
sched/fair: Add NOHZ balancer flag for nohz.next_balance updates
A following patch will trigger NOHZ idle balances as a means to update
nohz.next_balance. Vincent noted that blocked load updates can have
non-negligible overhead, which should be avoided if the intent is to only
update nohz.next_balance.
Add a new NOHZ balance kick flag, NOHZ_NEXT_KICK. Gate NOHZ blocked load
update by the presence of NOHZ_STATS_KICK - currently all NOHZ balance
kicks will have the NOHZ_STATS_KICK flag set, so no change in behaviour is
expected.
Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210823111700.2842997-2-valentin.schneider@arm.com
Diffstat (limited to 'kernel/sched/fair.c')
| -rw-r--r-- | kernel/sched/fair.c | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f6a05d9b5443..f4de7f555cbe 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10375,7 +10375,7 @@ static void nohz_balancer_kick(struct rq *rq) goto out; if (rq->nr_running >= 2) { - flags = NOHZ_KICK_MASK; + flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto out; } @@ -10389,7 +10389,7 @@ static void nohz_balancer_kick(struct rq *rq) * on. */ if (rq->cfs.h_nr_running >= 1 && check_cpu_capacity(rq, sd)) { - flags = NOHZ_KICK_MASK; + flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } } @@ -10403,7 +10403,7 @@ static void nohz_balancer_kick(struct rq *rq) */ for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) { if (sched_asym_prefer(i, cpu)) { - flags = NOHZ_KICK_MASK; + flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } } @@ -10416,7 +10416,7 @@ static void nohz_balancer_kick(struct rq *rq) * to run the misfit task on. */ if (check_misfit_status(rq, sd)) { - flags = NOHZ_KICK_MASK; + flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } @@ -10443,7 +10443,7 @@ static void nohz_balancer_kick(struct rq *rq) */ nr_busy = atomic_read(&sds->nr_busy_cpus); if (nr_busy > 1) { - flags = NOHZ_KICK_MASK; + flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto unlock; } } @@ -10605,7 +10605,8 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, * setting the flag, we are sure to not clear the state and not * check the load of an idle cpu. */ - WRITE_ONCE(nohz.has_blocked, 0); + if (flags & NOHZ_STATS_KICK) + WRITE_ONCE(nohz.has_blocked, 0); /* * Ensures that if we miss the CPU, we must see the has_blocked @@ -10627,13 +10628,15 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, * balancing owner will pick it up. */ if (need_resched()) { - has_blocked_load = true; + if (flags & NOHZ_STATS_KICK) + has_blocked_load = true; goto abort; } rq = cpu_rq(balance_cpu); - has_blocked_load |= update_nohz_stats(rq); + if (flags & NOHZ_STATS_KICK) + has_blocked_load |= update_nohz_stats(rq); /* * If time for next balance is due, @@ -10664,8 +10667,9 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags, if (likely(update_next_balance)) nohz.next_balance = next_balance; - WRITE_ONCE(nohz.next_blocked, - now + msecs_to_jiffies(LOAD_AVG_PERIOD)); + if (flags & NOHZ_STATS_KICK) + WRITE_ONCE(nohz.next_blocked, + now + msecs_to_jiffies(LOAD_AVG_PERIOD)); abort: /* There is still blocked load, enable periodic update */ |