From: tip-bot for Luca Abeni <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: mingo@kernel.org, mathieu.poirier@linaro.org,
claudio@evidence.eu.com, efault@gmx.de,
luca.abeni@santannapisa.it, tglx@linutronix.de,
joelaf@google.com, bristot@redhat.com,
linux-kernel@vger.kernel.org, juri.lelli@arm.com,
rostedt@goodmis.org, torvalds@linux-foundation.org,
hpa@zytor.com, tommaso.cucinotta@sssup.it, peterz@infradead.org
Subject: [tip:sched/core] sched/deadline: Do not reclaim the whole CPU bandwidth
Date: Thu, 8 Jun 2017 02:25:48 -0700 [thread overview]
Message-ID: <tip-4da3abcefe178c650033f371e94fa10e80bce167@git.kernel.org> (raw)
In-Reply-To: <1495138417-6203-6-git-send-email-luca.abeni@santannapisa.it>
Commit-ID: 4da3abcefe178c650033f371e94fa10e80bce167
Gitweb: http://git.kernel.org/tip/4da3abcefe178c650033f371e94fa10e80bce167
Author: Luca Abeni <luca.abeni@santannapisa.it>
AuthorDate: Thu, 18 May 2017 22:13:32 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 8 Jun 2017 10:31:51 +0200
sched/deadline: Do not reclaim the whole CPU bandwidth
Original GRUB tends to reclaim 100% of the CPU time... And this
allows a CPU hog to starve non-deadline tasks.
To address this issue, allow the scheduler to reclaim only a
specified fraction of CPU time, stored in the new "bw_ratio"
field of the dl runqueue structure.
Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-6-git-send-email-luca.abeni@santannapisa.it
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/core.c | 11 +++++++++++
kernel/sched/deadline.c | 12 +++++++++++-
kernel/sched/sched.h | 8 ++++++++
3 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b68a1fa..7abd064 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6759,6 +6759,16 @@ static int sched_dl_global_validate(void)
return ret;
}
+void init_dl_rq_bw_ratio(struct dl_rq *dl_rq)
+{
+ if (global_rt_runtime() == RUNTIME_INF) {
+ dl_rq->bw_ratio = 1 << RATIO_SHIFT;
+ } else {
+ dl_rq->bw_ratio = to_ratio(global_rt_runtime(),
+ global_rt_period()) >> (BW_SHIFT - RATIO_SHIFT);
+ }
+}
+
static void sched_dl_do_global(void)
{
u64 new_bw = -1;
@@ -6784,6 +6794,7 @@ static void sched_dl_do_global(void)
raw_spin_unlock_irqrestore(&dl_b->lock, flags);
rcu_read_unlock_sched();
+ init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
}
}
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0bee537..6a0614b 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -268,6 +268,7 @@ void init_dl_rq(struct dl_rq *dl_rq)
#endif
dl_rq->running_bw = 0;
+ init_dl_rq_bw_ratio(dl_rq);
}
#ifdef CONFIG_SMP
@@ -924,11 +925,20 @@ extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
* Uact is the (per-runqueue) active utilization.
* Since rq->dl.running_bw contains Uact * 2^BW_SHIFT, the result
* has to be shifted right by BW_SHIFT.
+ * To reclaim only a fraction Umax of the CPU time, the
+ * runtime accounting rule is modified as
+ * "dq = -Uact / Umax dt"; since rq->dl.bw_ratio contains
+ * 2^RATIO_SHIFT / Umax, delta is multiplied by bw_ratio and shifted
+ * right by RATIO_SHIFT.
+ * Since delta is a 64 bit variable, to have an overflow its value
+ * should be larger than 2^(64 - 20 - 8), which is more than 64 seconds.
+ * So, overflow is not an issue here.
*/
u64 grub_reclaim(u64 delta, struct rq *rq)
{
delta *= rq->dl.running_bw;
- delta >>= BW_SHIFT;
+ delta *= rq->dl.bw_ratio;
+ delta >>= BW_SHIFT + RATIO_SHIFT;
return delta;
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bb409ef..878fe75 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -565,6 +565,12 @@ struct dl_rq {
* task blocks
*/
u64 running_bw;
+
+ /*
+ * Inverse of the fraction of CPU utilization that can be reclaimed
+ * by the GRUB algorithm.
+ */
+ u64 bw_ratio;
};
#ifdef CONFIG_SMP
@@ -1495,9 +1501,11 @@ extern struct dl_bandwidth def_dl_bandwidth;
extern void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime);
extern void init_dl_task_timer(struct sched_dl_entity *dl_se);
extern void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se);
+extern void init_dl_rq_bw_ratio(struct dl_rq *dl_rq);
#define BW_SHIFT 20
#define BW_UNIT (1 << BW_SHIFT)
+#define RATIO_SHIFT 8
unsigned long to_ratio(u64 period, u64 runtime);
extern void init_entity_runnable_average(struct sched_entity *se);
next prev parent reply other threads:[~2017-06-08 9:31 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-18 20:13 [PATCH 00/10] CPU reclaiming for SCHED_DEADLINE luca abeni
2017-05-18 20:13 ` [PATCH 01/10] sched/deadline: track the active utilization luca abeni
2017-06-08 8:31 ` Ingo Molnar
2017-06-08 8:43 ` Luca Abeni
2017-06-08 9:05 ` Juri Lelli
2017-06-08 13:36 ` Steven Rostedt
2017-06-08 13:47 ` Juri Lelli
2017-06-08 9:23 ` [tip:sched/core] sched/deadline: Track " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 02/10] sched/deadline: improve the tracking of " luca abeni
2017-06-08 9:24 ` [tip:sched/core] sched/deadline: Improve " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 03/10] sched/deadline: fix the update of the total -deadline utilization luca abeni
2017-06-08 9:24 ` [tip:sched/core] sched/deadline: Fix " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 04/10] sched/deadline: implement GRUB accounting luca abeni
2017-06-08 9:25 ` [tip:sched/core] sched/deadline: Implement " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 05/10] sched/deadline: do not reclaim the whole CPU bandwidth luca abeni
2017-06-08 9:25 ` tip-bot for Luca Abeni [this message]
2017-05-18 20:13 ` [PATCH 06/10] sched/deadline: make GRUB a task's flag luca abeni
2017-06-08 9:26 ` [tip:sched/core] sched/deadline: Make " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 07/10] sched/deadline: track the "total rq utilization" too luca abeni
2017-06-08 9:26 ` [tip:sched/core] sched/deadline: Track " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 08/10] sched/deadline: base GRUB reclaiming on the inactive utilization luca abeni
2017-06-08 9:27 ` [tip:sched/core] sched/deadline: Base " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 09/10] sched/deadline: also reclaim bandwidth not used by dl tasks luca abeni
2017-06-08 9:28 ` [tip:sched/core] sched/deadline: Reclaim " tip-bot for Luca Abeni
2017-05-18 20:13 ` [PATCH 10/10] sched/deadline: documentation about GRUB reclaiming luca abeni
2017-06-08 9:28 ` [tip:sched/core] sched/deadline: Add " tip-bot for Claudio Scordino
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