diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2026-01-27 16:17:48 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-02-23 18:04:09 +0100 |
| commit | 9fe89f022c05d99c052d6bc088b82d4ff83bf463 (patch) | |
| tree | 3967b35e568221ab36e0617a86c6f5dbc5809c53 /kernel | |
| parent | 3b68df978133ac3d46d570af065a73debbb68248 (diff) | |
sched/fair: More complex proportional newidle balance
It turns out that a few workloads (easyWave, fio) have a fairly low
success rate on newidle balance, but still benefit greatly from having
it anyway.
Luckliky these workloads have a faily low newidle rate, so the cost if
doing the newidle is relatively low, even if unsuccessfull.
Add a simple rate based part to the newidle ratio compute, such that
low rate newidle will still have a high newidle ratio.
This cures the easyWave and fio workloads while not affecting the
schbench numbers either (which have a very high newidle rate).
Reported-by: Mario Roy <marioeroy@gmail.com>
Reported-by: "Mohamed Abuelfotoh, Hazem" <abuehaze@amazon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Mario Roy <marioeroy@gmail.com>
Tested-by: "Mohamed Abuelfotoh, Hazem" <abuehaze@amazon.com>
Link: https://patch.msgid.link/20260127151748.GA1079264@noisy.programming.kicks-ass.net
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 27 | ||||
| -rw-r--r-- | kernel/sched/features.h | 1 | ||||
| -rw-r--r-- | kernel/sched/topology.c | 3 |
3 files changed, 29 insertions, 2 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index bf948db905ed..66afa0ac7396 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12289,7 +12289,30 @@ static inline void update_newidle_stats(struct sched_domain *sd, unsigned int su sd->newidle_success += success; if (sd->newidle_call >= 1024) { - sd->newidle_ratio = sd->newidle_success; + u64 now = sched_clock(); + s64 delta = now - sd->newidle_stamp; + sd->newidle_stamp = now; + int ratio = 0; + + if (delta < 0) + delta = 0; + + if (sched_feat(NI_RATE)) { + /* + * ratio delta freq + * + * 1024 - 4 s - 128 Hz + * 512 - 2 s - 256 Hz + * 256 - 1 s - 512 Hz + * 128 - .5 s - 1024 Hz + * 64 - .25 s - 2048 Hz + */ + ratio = delta >> 22; + } + + ratio += sd->newidle_success; + + sd->newidle_ratio = min(1024, ratio); sd->newidle_call /= 2; sd->newidle_success /= 2; } @@ -12996,7 +13019,7 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf) if (sd->flags & SD_BALANCE_NEWIDLE) { unsigned int weight = 1; - if (sched_feat(NI_RANDOM)) { + if (sched_feat(NI_RANDOM) && sd->newidle_ratio < 1024) { /* * Throw a 1k sided dice; and only run * newidle_balance according to the success diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 136a6584be79..37d5928fa6dd 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -126,3 +126,4 @@ SCHED_FEAT(LATENCY_WARN, false) * Do newidle balancing proportional to its success rate using randomization. */ SCHED_FEAT(NI_RANDOM, true) +SCHED_FEAT(NI_RATE, true) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 32dcddaead82..061f8c85f555 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -4,6 +4,7 @@ */ #include <linux/sched/isolation.h> +#include <linux/sched/clock.h> #include <linux/bsearch.h> #include "sched.h" @@ -1642,6 +1643,7 @@ sd_init(struct sched_domain_topology_level *tl, struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu); int sd_id, sd_weight, sd_flags = 0; struct cpumask *sd_span; + u64 now = sched_clock(); sd_weight = cpumask_weight(tl->mask(tl, cpu)); @@ -1679,6 +1681,7 @@ sd_init(struct sched_domain_topology_level *tl, .newidle_call = 512, .newidle_success = 256, .newidle_ratio = 512, + .newidle_stamp = now, .max_newidle_lb_cost = 0, .last_decay_max_lb_cost = jiffies, |