Messages in this thread Patch in this message | | | From | Juri Lelli <> | Subject | [PATCH RFC 8/8] sched/deadline: make bandwidth enforcement scale-invariant | Date | Tue, 23 May 2017 09:53:51 +0100 |
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Apply frequency and cpu scale-invariance correction factor to bandwidth enforcement (similar to what we already do to fair utilization tracking).
Each delta_exec gets scaled considering current frequency and maximum cpu capacity; which means that the reservation runtime parameter (that need to be specified profiling the task execution at max frequency on biggest capacity core) gets thus scaled accordingly.
Signed-off-by: Juri Lelli <juri.lelli@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Luca Abeni <luca.abeni@santannapisa.it> Cc: Claudio Scordino <claudio@evidence.eu.com> --- Changes from RFD - either apply grub_reclaim or perform freq/cpu scaling; what's the correct thing to do it's actually very much up for discussion --- kernel/sched/deadline.c | 26 ++++++++++++++++++++++---- kernel/sched/fair.c | 2 -- kernel/sched/sched.h | 2 ++ 3 files changed, 24 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 5ee4fd9b1c7f..b6c3886478c3 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1008,7 +1008,8 @@ static void update_curr_dl(struct rq *rq) { struct task_struct *curr = rq->curr; struct sched_dl_entity *dl_se = &curr->dl; - u64 delta_exec; + u64 delta_exec, scaled_delta_exec; + int cpu = cpu_of(rq); if (!dl_task(curr) || !on_dl_rq(dl_se)) return; @@ -1042,9 +1043,26 @@ static void update_curr_dl(struct rq *rq) if (unlikely(dl_entity_is_special(dl_se))) return; - if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) - delta_exec = grub_reclaim(delta_exec, rq, &curr->dl); - dl_se->runtime -= delta_exec; + /* + * For tasks that participate in GRUB, we implement GRUB-PA: the + * spare reclaimed bandwidth is used to clock down frequency. + * + * For the others, we still need to scale reservation parameters + * according to current frequency and CPU maximum capacity. + */ + if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) { + scaled_delta_exec = grub_reclaim(delta_exec, + rq, + &curr->dl); + } else { + unsigned long scale_freq = arch_scale_freq_capacity(cpu); + unsigned long scale_cpu = arch_scale_cpu_capacity(NULL, cpu); + + scaled_delta_exec = cap_scale(delta_exec, scale_freq); + scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu); + } + + dl_se->runtime -= scaled_delta_exec; throttle: if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) { diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b0f31064bbbd..39224813e038 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2781,8 +2781,6 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) return c1 + c2 + c3; } -#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT) - /* * Accumulate the three separate parts of the sum; d1 the remainder * of the last (incomplete) period, d2 the span of full periods and d3 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index cc474c62cd18..019c46768ecb 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -155,6 +155,8 @@ static inline int task_has_dl_policy(struct task_struct *p) return dl_policy(p->policy); } +#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT) + static inline int dl_entity_is_special(struct sched_dl_entity *dl_se) { return dl_se->flags & SCHED_FLAG_SPECIAL; -- 2.11.0
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