From: "tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
Don Hiatt <dhiatt@digitalocean.com>,
Hongyu Ning <hongyu.ning@linux.intel.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] sched: Add core wide task selection and scheduling
Date: Wed, 12 May 2021 10:28:24 -0000 [thread overview]
Message-ID: <162081530440.29796.4267709137372239781.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210422123308.557559654@infradead.org>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 539f65125d20aacab54d02d77f10a839f45b09dc
Gitweb: https://git.kernel.org/tip/539f65125d20aacab54d02d77f10a839f45b09dc
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 17 Nov 2020 18:19:37 -05:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 12 May 2021 11:43:28 +02:00
sched: Add core wide task selection and scheduling
Instead of only selecting a local task, select a task for all SMT
siblings for every reschedule on the core (irrespective which logical
CPU does the reschedule).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.557559654@infradead.org
---
kernel/sched/core.c | 301 +++++++++++++++++++++++++++++++++++++++++-
kernel/sched/sched.h | 6 +-
2 files changed, 305 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c057d47..db763f4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5282,7 +5282,7 @@ static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
* Pick up the highest-prio task:
*/
static inline struct task_struct *
-pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+__pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
const struct sched_class *class;
struct task_struct *p;
@@ -5323,6 +5323,294 @@ restart:
}
#ifdef CONFIG_SCHED_CORE
+static inline bool is_task_rq_idle(struct task_struct *t)
+{
+ return (task_rq(t)->idle == t);
+}
+
+static inline bool cookie_equals(struct task_struct *a, unsigned long cookie)
+{
+ return is_task_rq_idle(a) || (a->core_cookie == cookie);
+}
+
+static inline bool cookie_match(struct task_struct *a, struct task_struct *b)
+{
+ if (is_task_rq_idle(a) || is_task_rq_idle(b))
+ return true;
+
+ return a->core_cookie == b->core_cookie;
+}
+
+// XXX fairness/fwd progress conditions
+/*
+ * Returns
+ * - NULL if there is no runnable task for this class.
+ * - the highest priority task for this runqueue if it matches
+ * rq->core->core_cookie or its priority is greater than max.
+ * - Else returns idle_task.
+ */
+static struct task_struct *
+pick_task(struct rq *rq, const struct sched_class *class, struct task_struct *max)
+{
+ struct task_struct *class_pick, *cookie_pick;
+ unsigned long cookie = rq->core->core_cookie;
+
+ class_pick = class->pick_task(rq);
+ if (!class_pick)
+ return NULL;
+
+ if (!cookie) {
+ /*
+ * If class_pick is tagged, return it only if it has
+ * higher priority than max.
+ */
+ if (max && class_pick->core_cookie &&
+ prio_less(class_pick, max))
+ return idle_sched_class.pick_task(rq);
+
+ return class_pick;
+ }
+
+ /*
+ * If class_pick is idle or matches cookie, return early.
+ */
+ if (cookie_equals(class_pick, cookie))
+ return class_pick;
+
+ cookie_pick = sched_core_find(rq, cookie);
+
+ /*
+ * If class > max && class > cookie, it is the highest priority task on
+ * the core (so far) and it must be selected, otherwise we must go with
+ * the cookie pick in order to satisfy the constraint.
+ */
+ if (prio_less(cookie_pick, class_pick) &&
+ (!max || prio_less(max, class_pick)))
+ return class_pick;
+
+ return cookie_pick;
+}
+
+static struct task_struct *
+pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ struct task_struct *next, *max = NULL;
+ const struct sched_class *class;
+ const struct cpumask *smt_mask;
+ bool need_sync;
+ int i, j, cpu;
+
+ if (!sched_core_enabled(rq))
+ return __pick_next_task(rq, prev, rf);
+
+ cpu = cpu_of(rq);
+
+ /* Stopper task is switching into idle, no need core-wide selection. */
+ if (cpu_is_offline(cpu)) {
+ /*
+ * Reset core_pick so that we don't enter the fastpath when
+ * coming online. core_pick would already be migrated to
+ * another cpu during offline.
+ */
+ rq->core_pick = NULL;
+ return __pick_next_task(rq, prev, rf);
+ }
+
+ /*
+ * If there were no {en,de}queues since we picked (IOW, the task
+ * pointers are all still valid), and we haven't scheduled the last
+ * pick yet, do so now.
+ *
+ * rq->core_pick can be NULL if no selection was made for a CPU because
+ * it was either offline or went offline during a sibling's core-wide
+ * selection. In this case, do a core-wide selection.
+ */
+ if (rq->core->core_pick_seq == rq->core->core_task_seq &&
+ rq->core->core_pick_seq != rq->core_sched_seq &&
+ rq->core_pick) {
+ WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq);
+
+ next = rq->core_pick;
+ if (next != prev) {
+ put_prev_task(rq, prev);
+ set_next_task(rq, next);
+ }
+
+ rq->core_pick = NULL;
+ return next;
+ }
+
+ put_prev_task_balance(rq, prev, rf);
+
+ smt_mask = cpu_smt_mask(cpu);
+
+ /*
+ * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
+ *
+ * @task_seq guards the task state ({en,de}queues)
+ * @pick_seq is the @task_seq we did a selection on
+ * @sched_seq is the @pick_seq we scheduled
+ *
+ * However, preemptions can cause multiple picks on the same task set.
+ * 'Fix' this by also increasing @task_seq for every pick.
+ */
+ rq->core->core_task_seq++;
+ need_sync = !!rq->core->core_cookie;
+
+ /* reset state */
+ rq->core->core_cookie = 0UL;
+ for_each_cpu(i, smt_mask) {
+ struct rq *rq_i = cpu_rq(i);
+
+ rq_i->core_pick = NULL;
+
+ if (rq_i->core_forceidle) {
+ need_sync = true;
+ rq_i->core_forceidle = false;
+ }
+
+ if (i != cpu)
+ update_rq_clock(rq_i);
+ }
+
+ /*
+ * Try and select tasks for each sibling in decending sched_class
+ * order.
+ */
+ for_each_class(class) {
+again:
+ for_each_cpu_wrap(i, smt_mask, cpu) {
+ struct rq *rq_i = cpu_rq(i);
+ struct task_struct *p;
+
+ if (rq_i->core_pick)
+ continue;
+
+ /*
+ * If this sibling doesn't yet have a suitable task to
+ * run; ask for the most elegible task, given the
+ * highest priority task already selected for this
+ * core.
+ */
+ p = pick_task(rq_i, class, max);
+ if (!p) {
+ /*
+ * If there weren't no cookies; we don't need to
+ * bother with the other siblings.
+ * If the rest of the core is not running a tagged
+ * task, i.e. need_sync == 0, and the current CPU
+ * which called into the schedule() loop does not
+ * have any tasks for this class, skip selecting for
+ * other siblings since there's no point. We don't skip
+ * for RT/DL because that could make CFS force-idle RT.
+ */
+ if (i == cpu && !need_sync && class == &fair_sched_class)
+ goto next_class;
+
+ continue;
+ }
+
+ /*
+ * Optimize the 'normal' case where there aren't any
+ * cookies and we don't need to sync up.
+ */
+ if (i == cpu && !need_sync && !p->core_cookie) {
+ next = p;
+ goto done;
+ }
+
+ rq_i->core_pick = p;
+
+ /*
+ * If this new candidate is of higher priority than the
+ * previous; and they're incompatible; we need to wipe
+ * the slate and start over. pick_task makes sure that
+ * p's priority is more than max if it doesn't match
+ * max's cookie.
+ *
+ * NOTE: this is a linear max-filter and is thus bounded
+ * in execution time.
+ */
+ if (!max || !cookie_match(max, p)) {
+ struct task_struct *old_max = max;
+
+ rq->core->core_cookie = p->core_cookie;
+ max = p;
+
+ if (old_max) {
+ for_each_cpu(j, smt_mask) {
+ if (j == i)
+ continue;
+
+ cpu_rq(j)->core_pick = NULL;
+ }
+ goto again;
+ } else {
+ /*
+ * Once we select a task for a cpu, we
+ * should not be doing an unconstrained
+ * pick because it might starve a task
+ * on a forced idle cpu.
+ */
+ need_sync = true;
+ }
+
+ }
+ }
+next_class:;
+ }
+
+ rq->core->core_pick_seq = rq->core->core_task_seq;
+ next = rq->core_pick;
+ rq->core_sched_seq = rq->core->core_pick_seq;
+
+ /* Something should have been selected for current CPU */
+ WARN_ON_ONCE(!next);
+
+ /*
+ * Reschedule siblings
+ *
+ * NOTE: L1TF -- at this point we're no longer running the old task and
+ * sending an IPI (below) ensures the sibling will no longer be running
+ * their task. This ensures there is no inter-sibling overlap between
+ * non-matching user state.
+ */
+ for_each_cpu(i, smt_mask) {
+ struct rq *rq_i = cpu_rq(i);
+
+ /*
+ * An online sibling might have gone offline before a task
+ * could be picked for it, or it might be offline but later
+ * happen to come online, but its too late and nothing was
+ * picked for it. That's Ok - it will pick tasks for itself,
+ * so ignore it.
+ */
+ if (!rq_i->core_pick)
+ continue;
+
+ if (is_task_rq_idle(rq_i->core_pick) && rq_i->nr_running)
+ rq_i->core_forceidle = true;
+
+ if (i == cpu) {
+ rq_i->core_pick = NULL;
+ continue;
+ }
+
+ /* Did we break L1TF mitigation requirements? */
+ WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick));
+
+ if (rq_i->curr == rq_i->core_pick) {
+ rq_i->core_pick = NULL;
+ continue;
+ }
+
+ resched_curr(rq_i);
+ }
+
+done:
+ set_next_task(rq, next);
+ return next;
+}
static inline void sched_core_cpu_starting(unsigned int cpu)
{
@@ -5354,6 +5642,12 @@ static inline void sched_core_cpu_starting(unsigned int cpu)
static inline void sched_core_cpu_starting(unsigned int cpu) {}
+static struct task_struct *
+pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+ return __pick_next_task(rq, prev, rf);
+}
+
#endif /* CONFIG_SCHED_CORE */
/*
@@ -8609,7 +8903,12 @@ void __init sched_init(void)
#ifdef CONFIG_SCHED_CORE
rq->core = NULL;
+ rq->core_pick = NULL;
rq->core_enabled = 0;
+ rq->core_tree = RB_ROOT;
+ rq->core_forceidle = false;
+
+ rq->core_cookie = 0UL;
#endif
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e43a217..dd44a31 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1079,11 +1079,16 @@ struct rq {
#ifdef CONFIG_SCHED_CORE
/* per rq */
struct rq *core;
+ struct task_struct *core_pick;
unsigned int core_enabled;
+ unsigned int core_sched_seq;
struct rb_root core_tree;
+ unsigned char core_forceidle;
/* shared state */
unsigned int core_task_seq;
+ unsigned int core_pick_seq;
+ unsigned long core_cookie;
#endif
};
@@ -2060,7 +2065,6 @@ static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
static inline void set_next_task(struct rq *rq, struct task_struct *next)
{
- WARN_ON_ONCE(rq->curr != next);
next->sched_class->set_next_task(rq, next, false);
}
next prev parent reply other threads:[~2021-05-12 10:28 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 12:04 [PATCH 00/19] sched: Core Scheduling Peter Zijlstra
2021-04-22 12:05 ` [PATCH 01/19] sched/fair: Add a few assertions Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-05-13 8:56 ` Ning, Hongyu
2021-04-22 12:05 ` [PATCH 02/19] sched: Provide raw_spin_rq_*lock*() helpers Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 03/19] sched: Wrap rq::lock access Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 04/19] sched: Prepare for Core-wide rq->lock Peter Zijlstra
2021-04-24 1:22 ` Josh Don
2021-04-26 8:31 ` Peter Zijlstra
2021-04-26 22:21 ` Josh Don
2021-04-27 17:10 ` Don Hiatt
2021-04-27 23:35 ` Josh Don
2021-04-28 1:03 ` Aubrey Li
2021-04-28 6:05 ` Aubrey Li
2021-04-28 10:57 ` Aubrey Li
2021-04-28 16:41 ` Don Hiatt
2021-04-29 20:48 ` Josh Don
2021-04-29 21:09 ` Don Hiatt
2021-04-29 23:22 ` Josh Don
2021-04-30 16:18 ` Don Hiatt
2021-04-30 8:26 ` Aubrey Li
2021-04-28 16:04 ` Don Hiatt
2021-04-27 23:30 ` Josh Don
2021-04-28 9:13 ` Peter Zijlstra
2021-04-28 10:35 ` Aubrey Li
2021-04-28 11:03 ` Peter Zijlstra
2021-04-28 14:18 ` Paul E. McKenney
2021-04-29 20:11 ` Josh Don
2021-05-03 19:17 ` Peter Zijlstra
2021-04-28 7:13 ` Peter Zijlstra
2021-04-28 6:02 ` Aubrey Li
2021-04-29 8:03 ` Aubrey Li
2021-04-29 20:39 ` Josh Don
2021-04-30 8:20 ` Aubrey Li
2021-04-30 8:48 ` Josh Don
2021-04-30 14:15 ` Aubrey Li
2021-05-04 7:38 ` Peter Zijlstra
2021-05-05 16:20 ` Don Hiatt
2021-05-06 10:25 ` Peter Zijlstra
2021-05-07 9:50 ` [PATCH v2 " Peter Zijlstra
2021-05-08 8:07 ` Aubrey Li
2021-05-12 9:07 ` Peter Zijlstra
2021-04-22 12:05 ` [PATCH 05/19] sched: " Peter Zijlstra
2021-05-07 9:50 ` [PATCH v2 " Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 06/19] sched: Optimize rq_lockp() usage Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 07/19] sched: Allow sched_core_put() from atomic context Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 08/19] sched: Introduce sched_class::pick_task() Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 09/19] sched: Basic tracking of matching tasks Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 10/19] sched: Add core wide task selection and scheduling Peter Zijlstra
2021-05-12 10:28 ` tip-bot2 for Peter Zijlstra [this message]
2021-04-22 12:05 ` [PATCH 11/19] sched/fair: Fix forced idle sibling starvation corner case Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Vineeth Pillai
2021-04-22 12:05 ` [PATCH 12/19] sched: Fix priority inversion of cookied task with sibling Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Joel Fernandes (Google)
2021-04-22 12:05 ` [PATCH 13/19] sched/fair: Snapshot the min_vruntime of CPUs on force idle Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Joel Fernandes (Google)
2021-04-22 12:05 ` [PATCH 14/19] sched: Trivial forced-newidle balancer Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 15/19] sched: Migration changes for core scheduling Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Aubrey Li
2021-04-22 12:05 ` [PATCH 16/19] sched: Trivial core scheduling cookie management Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 17/19] sched: Inherit task cookie on fork() Peter Zijlstra
2021-05-10 16:06 ` Joel Fernandes
2021-05-10 16:22 ` Chris Hyser
2021-05-10 20:47 ` Joel Fernandes
2021-05-10 21:38 ` Chris Hyser
2021-05-12 9:05 ` Peter Zijlstra
2021-05-12 20:20 ` Josh Don
2021-05-12 21:07 ` Don Hiatt
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 18/19] sched: prctl() core-scheduling interface Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Chris Hyser
2021-06-14 23:36 ` [PATCH 18/19] " Josh Don
2021-06-15 11:31 ` Joel Fernandes
2021-08-05 16:53 ` Eugene Syromiatnikov
2021-08-05 17:00 ` Peter Zijlstra
2021-08-17 15:15 ` Eugene Syromiatnikov
2021-08-17 15:52 ` Peter Zijlstra
2021-08-17 23:17 ` Eugene Syromiatnikov
2021-08-19 11:09 ` [PATCH] sched: Fix Core-wide rq->lock for uninitialized CPUs Peter Zijlstra
2021-08-19 15:50 ` Tao Zhou
2021-08-19 16:19 ` Eugene Syromiatnikov
2021-08-20 0:18 ` Josh Don
2021-08-20 10:02 ` Peter Zijlstra
2021-08-23 9:07 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-04-22 12:05 ` [PATCH 19/19] kselftest: Add test for core sched prctl interface Peter Zijlstra
2021-05-12 10:28 ` [tip: sched/core] " tip-bot2 for Chris Hyser
2021-04-22 16:43 ` [PATCH 00/19] sched: Core Scheduling Don Hiatt
2021-04-22 17:29 ` Peter Zijlstra
2021-04-30 6:47 ` Ning, Hongyu
2021-05-06 10:29 ` Peter Zijlstra
2021-05-06 12:53 ` Ning, Hongyu
2021-05-07 18:02 ` Joel Fernandes
2021-05-10 16:16 ` Vincent Guittot
2021-05-11 7:00 ` Vincent Guittot
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