From: Vincent Guittot <vincent.guittot@linaro.org>
To: peterz@infradead.org, mingo@kernel.org,
linux-kernel@vger.kernel.org, preeti@linux.vnet.ibm.com,
Morten.Rasmussen@arm.com, kamalesh@linux.vnet.ibm.com,
linux-arm-kernel@lists.infradead.org
Cc: riel@redhat.com, efault@gmx.de, nicolas.pitre@linaro.org,
linaro-kernel@lists.linaro.org,
Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH v9 05/10] sched: make scale_rt invariant with frequency
Date: Mon, 3 Nov 2014 17:54:42 +0100 [thread overview]
Message-ID: <1415033687-23294-6-git-send-email-vincent.guittot@linaro.org> (raw)
In-Reply-To: <1415033687-23294-1-git-send-email-vincent.guittot@linaro.org>
The average running time of RT tasks is used to estimate the remaining compute
capacity for CFS tasks. This remaining capacity is the original capacity scaled
down by a factor (aka scale_rt_capacity). This estimation of available capacity
must also be invariant with frequency scaling.
A frequency scaling factor is applied on the running time of the RT tasks for
computing scale_rt_capacity.
In sched_rt_avg_update, we scale the RT execution time like below:
rq->rt_avg += rt_delta * arch_scale_freq_capacity() >> SCHED_CAPACITY_SHIFT
Then, scale_rt_capacity can be summarized by:
scale_rt_capacity = SCHED_CAPACITY_SCALE -
((rq->rt_avg << SCHED_CAPACITY_SHIFT) / period)
We can optimize by removing right and left shift in the computation of rq->rt_avg
and scale_rt_capacity
The call to arch_scale_frequency_capacity in the rt scheduling path might be
a concern for RT folks because I'm not sure whether we can rely on
arch_scale_freq_capacity to be short and efficient ?
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/fair.c | 17 +++++------------
kernel/sched/sched.h | 4 +++-
2 files changed, 8 insertions(+), 13 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a5039da..b37c27b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5785,7 +5785,7 @@ unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
static unsigned long scale_rt_capacity(int cpu)
{
struct rq *rq = cpu_rq(cpu);
- u64 total, available, age_stamp, avg;
+ u64 total, used, age_stamp, avg;
s64 delta;
/*
@@ -5801,19 +5801,12 @@ static unsigned long scale_rt_capacity(int cpu)
total = sched_avg_period() + delta;
- if (unlikely(total < avg)) {
- /* Ensures that capacity won't end up being negative */
- available = 0;
- } else {
- available = total - avg;
- }
+ used = div_u64(avg, total);
- if (unlikely((s64)total < SCHED_CAPACITY_SCALE))
- total = SCHED_CAPACITY_SCALE;
+ if (likely(used < SCHED_CAPACITY_SCALE))
+ return SCHED_CAPACITY_SCALE - used;
- total >>= SCHED_CAPACITY_SHIFT;
-
- return div_u64(available, total);
+ return 1;
}
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c34bd11..fc5b152 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1312,9 +1312,11 @@ static inline int hrtick_enabled(struct rq *rq)
#ifdef CONFIG_SMP
extern void sched_avg_update(struct rq *rq);
+extern unsigned long arch_scale_freq_capacity(struct sched_domain *sd, int cpu);
+
static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
{
- rq->rt_avg += rt_delta;
+ rq->rt_avg += rt_delta * arch_scale_freq_capacity(NULL, cpu_of(rq));
sched_avg_update(rq);
}
#else
--
1.9.1
next prev parent reply other threads:[~2014-11-03 16:56 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-03 16:54 [PATCH v9 00/10] sched: consolidation of CPU capacity and usage Vincent Guittot
2014-11-03 16:54 ` [PATCH v9 01/10] sched: add utilization_avg_contrib Vincent Guittot
2014-11-21 12:34 ` Morten Rasmussen
2014-11-24 14:04 ` Vincent Guittot
2014-11-24 17:34 ` Morten Rasmussen
2014-11-03 16:54 ` [PATCH v9 02/10] sched: Track group sched_entity usage contributions Vincent Guittot
2014-11-21 12:35 ` Morten Rasmussen
2014-11-24 14:04 ` Vincent Guittot
2014-11-24 15:39 ` Morten Rasmussen
2014-11-03 16:54 ` [PATCH v9 03/10] sched: remove frequency scaling from cpu_capacity Vincent Guittot
2014-11-21 12:35 ` Morten Rasmussen
2014-11-03 16:54 ` [PATCH v9 04/10] sched: Make sched entity usage tracking scale-invariant Vincent Guittot
2014-11-21 12:35 ` Morten Rasmussen
2014-11-26 16:05 ` Dietmar Eggemann
2014-11-03 16:54 ` Vincent Guittot [this message]
2014-11-21 12:35 ` [PATCH v9 05/10] sched: make scale_rt invariant with frequency Morten Rasmussen
2014-11-24 14:24 ` Vincent Guittot
2014-11-24 17:05 ` Morten Rasmussen
2014-11-25 13:48 ` Vincent Guittot
2014-11-26 11:57 ` Morten Rasmussen
2014-11-25 2:24 ` Wanpeng Li
2014-11-25 13:52 ` Vincent Guittot
2014-11-26 5:18 ` Wanpeng Li
2014-11-26 8:27 ` Vincent Guittot
2014-11-03 16:54 ` [PATCH v9 06/10] sched: add per rq cpu_capacity_orig Vincent Guittot
2014-11-03 16:54 ` [PATCH v9 07/10] sched: get CPU's usage statistic Vincent Guittot
2014-11-21 12:36 ` Morten Rasmussen
2014-11-03 16:54 ` [PATCH v9 08/10] sched: replace capacity_factor by usage Vincent Guittot
2014-11-19 15:15 ` pang.xunlei
2014-11-19 17:30 ` Vincent Guittot
2014-11-21 12:37 ` Morten Rasmussen
2014-11-24 14:41 ` Vincent Guittot
2014-11-24 17:16 ` Morten Rasmussen
2014-11-03 16:54 ` [PATCH v9 09/10] sched: add SD_PREFER_SIBLING for SMT level Vincent Guittot
2014-11-03 16:54 ` [PATCH v9 10/10] sched: move cfs task on a CPU with higher capacity Vincent Guittot
2014-11-21 12:37 ` Morten Rasmussen
2014-11-24 14:45 ` Vincent Guittot
2014-11-24 17:30 ` Morten Rasmussen
2014-11-21 12:34 ` [PATCH v9 00/10] sched: consolidation of CPU capacity and usage Morten Rasmussen
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