Messages in this thread Patch in this message | | | From | Dietmar Eggemann <> | Subject | [RFC PATCH 1/1] sched/pelt: Introduce PELT multiplier | Date | Mon, 29 Aug 2022 07:54:50 +0200 |
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From: Vincent Donnefort <vincent.donnefort@arm.com>
The new sysctl sched_pelt_multiplier allows a user to set a clock multiplier to x2 or x4 (x1 being the default). This clock multiplier artificially speeds up PELT ramp up/down similarly to use a faster half-life than the default 32ms.
- x1: 32ms half-life - x2: 16ms half-life - x4: 8ms half-life
Internally, a new clock is created: rq->clock_task_mult. It sits in the clock hierarchy between rq->clock_task and rq->clock_pelt.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> --- kernel/sched/core.c | 2 +- kernel/sched/pelt.c | 60 ++++++++++++++++++++++++++++++++++++++++++++ kernel/sched/pelt.h | 42 ++++++++++++++++++++++++++++--- kernel/sched/sched.h | 1 + 4 files changed, 100 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 603a80ec9b0e..6203cead4ad3 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -727,7 +727,7 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) update_irq_load_avg(rq, irq_delta + steal); #endif - update_rq_clock_pelt(rq, delta); + update_rq_clock_task_mult(rq, delta); } void update_rq_clock(struct rq *rq) diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c index 9adfc4744544..9fa853a64269 100644 --- a/kernel/sched/pelt.c +++ b/kernel/sched/pelt.c @@ -472,3 +472,63 @@ int update_irq_load_avg(struct rq *rq, u64 running) return ret; } #endif + +__read_mostly unsigned int sched_pelt_lshift; + +#ifdef CONFIG_SYSCTL +static unsigned int sysctl_sched_pelt_multiplier = 1; + +int sched_pelt_multiplier(struct ctl_table *table, int write, void *buffer, + size_t *lenp, loff_t *ppos) +{ + static DEFINE_MUTEX(mutex); + unsigned int old; + int ret; + + mutex_lock(&mutex); + old = sysctl_sched_pelt_multiplier; + ret = proc_dointvec(table, write, buffer, lenp, ppos); + if (ret) + goto undo; + if (!write) + goto done; + + switch (sysctl_sched_pelt_multiplier) { + case 1: + fallthrough; + case 2: + fallthrough; + case 4: + WRITE_ONCE(sched_pelt_lshift, + sysctl_sched_pelt_multiplier >> 1); + goto done; + default: + ret = -EINVAL; + } + +undo: + sysctl_sched_pelt_multiplier = old; +done: + mutex_unlock(&mutex); + + return ret; +} + +static struct ctl_table sched_pelt_sysctls[] = { + { + .procname = "sched_pelt_multiplier", + .data = &sysctl_sched_pelt_multiplier, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sched_pelt_multiplier, + }, + {} +}; + +static int __init sched_pelt_sysctl_init(void) +{ + register_sysctl_init("kernel", sched_pelt_sysctls); + return 0; +} +late_initcall(sched_pelt_sysctl_init); +#endif diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h index 3a0e0dc28721..9b35b5072bae 100644 --- a/kernel/sched/pelt.h +++ b/kernel/sched/pelt.h @@ -61,6 +61,14 @@ static inline void cfs_se_util_change(struct sched_avg *avg) WRITE_ONCE(avg->util_est.enqueued, enqueued); } +static inline u64 rq_clock_task_mult(struct rq *rq) +{ + lockdep_assert_rq_held(rq); + assert_clock_updated(rq); + + return rq->clock_task_mult; +} + static inline u64 rq_clock_pelt(struct rq *rq) { lockdep_assert_rq_held(rq); @@ -72,7 +80,7 @@ static inline u64 rq_clock_pelt(struct rq *rq) /* The rq is idle, we can sync to clock_task */ static inline void _update_idle_rq_clock_pelt(struct rq *rq) { - rq->clock_pelt = rq_clock_task(rq); + rq->clock_pelt = rq_clock_task_mult(rq); u64_u32_store(rq->clock_idle, rq_clock(rq)); /* Paired with smp_rmb in migrate_se_pelt_lag() */ @@ -121,6 +129,27 @@ static inline void update_rq_clock_pelt(struct rq *rq, s64 delta) rq->clock_pelt += delta; } +extern unsigned int sched_pelt_lshift; + +/* + * absolute time |1 |2 |3 |4 |5 |6 | + * @ mult = 1 --------****************--------****************- + * @ mult = 2 --------********----------------********--------- + * @ mult = 4 --------****--------------------****------------- + * clock task mult + * @ mult = 2 | | |2 |3 | | | | |5 |6 | | | + * @ mult = 4 | | | | |2|3| | | | | | | | | | |5|6| | | | | | | + * + */ +static inline void update_rq_clock_task_mult(struct rq *rq, s64 delta) +{ + delta <<= READ_ONCE(sched_pelt_lshift); + + rq->clock_task_mult += delta; + + update_rq_clock_pelt(rq, delta); +} + /* * When rq becomes idle, we have to check if it has lost idle time * because it was fully busy. A rq is fully used when the /Sum util_sum @@ -147,7 +176,7 @@ static inline void update_idle_rq_clock_pelt(struct rq *rq) * rq's clock_task. */ if (util_sum >= divider) - rq->lost_idle_time += rq_clock_task(rq) - rq->clock_pelt; + rq->lost_idle_time += rq_clock_task_mult(rq) - rq->clock_pelt; _update_idle_rq_clock_pelt(rq); } @@ -218,13 +247,18 @@ update_irq_load_avg(struct rq *rq, u64 running) return 0; } -static inline u64 rq_clock_pelt(struct rq *rq) +static inline u64 rq_clock_task_mult(struct rq *rq) { return rq_clock_task(rq); } +static inline u64 rq_clock_pelt(struct rq *rq) +{ + return rq_clock_task_mult(rq); +} + static inline void -update_rq_clock_pelt(struct rq *rq, s64 delta) { } +update_rq_clock_task_mult(struct rq *rq, s64 delta) { } static inline void update_idle_rq_clock_pelt(struct rq *rq) { } diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index da17be6f27fd..62fc3cf10ea7 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1007,6 +1007,7 @@ struct rq { u64 clock; /* Ensure that all clocks are in the same cache line */ u64 clock_task ____cacheline_aligned; + u64 clock_task_mult; u64 clock_pelt; unsigned long lost_idle_time; u64 clock_pelt_idle; -- 2.25.1
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