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From: Aaron Lu <aaron.lu@linux.alibaba.com>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: "Peter Zijlstra" <peterz@infradead.org>,
	"Julien Desfossez" <jdesfossez@digitalocean.com>,
	"Li, Aubrey" <aubrey.li@linux.intel.com>,
	"Aubrey Li" <aubrey.intel@gmail.com>,
	"Subhra Mazumdar" <subhra.mazumdar@oracle.com>,
	"Vineeth Remanan Pillai" <vpillai@digitalocean.com>,
	"Nishanth Aravamudan" <naravamudan@digitalocean.com>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Paul Turner" <pjt@google.com>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	"Linux List Kernel Mailing" <linux-kernel@vger.kernel.org>,
	"Frédéric Weisbecker" <fweisbec@gmail.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Greg Kerr" <kerrnel@google.com>, "Phil Auld" <pauld@redhat.com>,
	"Valentin Schneider" <valentin.schneider@arm.com>,
	"Mel Gorman" <mgorman@techsingularity.net>,
	"Pawan Gupta" <pawan.kumar.gupta@linux.intel.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [RFC PATCH v3 00/16] Core scheduling v3
Date: Sat, 10 Aug 2019 22:15:56 +0800	[thread overview]
Message-ID: <20190810141556.GA73644@aaronlu> (raw)
In-Reply-To: <b7a83fcb-5c34-9794-5688-55c52697fd84@linux.intel.com>

On Thu, Aug 08, 2019 at 02:42:57PM -0700, Tim Chen wrote:
> On 8/8/19 10:27 AM, Tim Chen wrote:
> > On 8/7/19 11:47 PM, Aaron Lu wrote:
> >> On Tue, Aug 06, 2019 at 02:19:57PM -0700, Tim Chen wrote:
> >>> +void account_core_idletime(struct task_struct *p, u64 exec)
> >>> +{
> >>> +	const struct cpumask *smt_mask;
> >>> +	struct rq *rq;
> >>> +	bool force_idle, refill;
> >>> +	int i, cpu;
> >>> +
> >>> +	rq = task_rq(p);
> >>> +	if (!sched_core_enabled(rq) || !p->core_cookie)
> >>> +		return;
> >>
> >> I don't see why return here for untagged task. Untagged task can also
> >> preempt tagged task and force a CPU thread enter idle state.
> >> Untagged is just another tag to me, unless we want to allow untagged
> >> task to coschedule with a tagged task.
> > 
> > You are right.  This needs to be fixed.
> > 
> 
> Here's the updated patchset, including Aaron's fix and also
> added accounting of force idle time by deadline and rt tasks.

I have two other small changes that I think are worth sending out.

The first simplify logic in pick_task() and the 2nd avoid task pick all
over again when max is preempted. I also refined the previous hack patch to
make schedule always happen only for root cfs rq. Please see below for
details, thanks.

patch1:

From cea56db35fe9f393c357cdb1bdcb2ef9b56cfe97 Mon Sep 17 00:00:00 2001
From: Aaron Lu <ziqian.lzq@antfin.com>
Date: Mon, 5 Aug 2019 21:21:25 +0800
Subject: [PATCH 1/3] sched/core: simplify pick_task()

No need to special case !cookie case in pick_task(), we just need to
make it possible to return idle in sched_core_find() for !cookie query.
And cookie_pick will always have less priority than class_pick, so
remove the redundant check of prio_less(cookie_pick, class_pick).

Signed-off-by: Aaron Lu <ziqian.lzq@antfin.com>
---
 kernel/sched/core.c | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90655c9ad937..84fec9933b74 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -186,6 +186,8 @@ static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
 	 * The idle task always matches any cookie!
 	 */
 	match = idle_sched_class.pick_task(rq);
+	if (!cookie)
+		goto out;
 
 	while (node) {
 		node_task = container_of(node, struct task_struct, core_node);
@@ -199,7 +201,7 @@ static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
 			node = node->rb_left;
 		}
 	}
-
+out:
 	return match;
 }
 
@@ -3657,18 +3659,6 @@ pick_task(struct rq *rq, const struct sched_class *class, struct task_struct *ma
 	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.
 	 */
@@ -3682,8 +3672,7 @@ pick_task(struct rq *rq, const struct sched_class *class, struct task_struct *ma
 	 * 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)))
+	if (!max || prio_less(max, class_pick))
 		return class_pick;
 
 	return cookie_pick;
-- 
2.19.1.3.ge56e4f7

patch2:

From 487950dc53a40d5c566602f775ce46a0bab7a412 Mon Sep 17 00:00:00 2001
From: Aaron Lu <ziqian.lzq@antfin.com>
Date: Fri, 9 Aug 2019 14:48:01 +0800
Subject: [PATCH 2/3] sched/core: no need to pick again after max is preempted

When sibling's task preempts current max, there is no need to do the
pick all over again - the preempted cpu could just pick idle and done.

Signed-off-by: Aaron Lu <ziqian.lzq@antfin.com>
---
 kernel/sched/core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 84fec9933b74..e88583860abe 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3756,7 +3756,6 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 	 * 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;
@@ -3828,10 +3827,10 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 						if (j == i)
 							continue;
 
-						cpu_rq(j)->core_pick = NULL;
+						cpu_rq(j)->core_pick = idle_sched_class.pick_task(cpu_rq(j));
 					}
 					occ = 1;
-					goto again;
+					goto out;
 				} else {
 					/*
 					 * Once we select a task for a cpu, we
@@ -3846,7 +3845,7 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 		}
 next_class:;
 	}
-
+out:
 	rq->core->core_pick_seq = rq->core->core_task_seq;
 	next = rq->core_pick;
 	rq->core_sched_seq = rq->core->core_pick_seq;
-- 
2.19.1.3.ge56e4f7

patch3:

From 2d396d99e0dd7157b0b4f7a037c8b84ed135ea56 Mon Sep 17 00:00:00 2001
From: Aaron Lu <ziqian.lzq@antfin.com>
Date: Thu, 25 Jul 2019 19:57:21 +0800
Subject: [PATCH 3/3] sched/fair: make tick based schedule always happen

When a hyperthread is forced idle and the other hyperthread has a single
CPU intensive task running, the running task can occupy the hyperthread
for a long time with no scheduling point and starve the other
hyperthread.

Fix this temporarily by always checking if the task has exceed its
timeslice and if so, for root cfs_rq, do a schedule.

Signed-off-by: Aaron Lu <ziqian.lzq@antfin.com>
---
 kernel/sched/fair.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 26d29126d6a5..b1f0defdad91 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4011,6 +4011,9 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 		return;
 	}
 
+	if (cfs_rq->nr_running <= 1)
+		return;
+
 	/*
 	 * Ensure that a task that missed wakeup preemption by a
 	 * narrow margin doesn't have to wait for a full slice.
@@ -4179,7 +4182,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 		return;
 #endif
 
-	if (cfs_rq->nr_running > 1)
+	if (cfs_rq->nr_running > 1 || cfs_rq->tg == &root_task_group)
 		check_preempt_tick(cfs_rq, curr);
 }
 
-- 
2.19.1.3.ge56e4f7


  reply	other threads:[~2019-08-10 14:16 UTC|newest]

Thread overview: 161+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-29 20:36 Vineeth Remanan Pillai
2019-05-29 20:36 ` [RFC PATCH v3 01/16] stop_machine: Fix stop_cpus_in_progress ordering Vineeth Remanan Pillai
2019-08-08 10:54   ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-08-26 16:19   ` [RFC PATCH v3 01/16] " mark gross
2019-08-26 16:59     ` Peter Zijlstra
2019-05-29 20:36 ` [RFC PATCH v3 02/16] sched: Fix kerneldoc comment for ia64_set_curr_task Vineeth Remanan Pillai
2019-08-08 10:55   ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-08-26 16:20   ` [RFC PATCH v3 02/16] " mark gross
2019-05-29 20:36 ` [RFC PATCH v3 03/16] sched: Wrap rq::lock access Vineeth Remanan Pillai
2019-05-29 20:36 ` [RFC PATCH v3 04/16] sched/{rt,deadline}: Fix set_next_task vs pick_next_task Vineeth Remanan Pillai
2019-08-08 10:55   ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-05-29 20:36 ` [RFC PATCH v3 05/16] sched: Add task_struct pointer to sched_class::set_curr_task Vineeth Remanan Pillai
2019-08-08 10:57   ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-05-29 20:36 ` [RFC PATCH v3 06/16] sched/fair: Export newidle_balance() Vineeth Remanan Pillai
2019-08-08 10:58   ` [tip:sched/core] sched/fair: Expose newidle_balance() tip-bot for Peter Zijlstra
2019-05-29 20:36 ` [RFC PATCH v3 07/16] sched: Allow put_prev_task() to drop rq->lock Vineeth Remanan Pillai
2019-08-08 10:58   ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-08-26 16:51   ` [RFC PATCH v3 07/16] " mark gross
2019-05-29 20:36 ` [RFC PATCH v3 08/16] sched: Rework pick_next_task() slow-path Vineeth Remanan Pillai
2019-08-08 10:59   ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-08-26 17:01   ` [RFC PATCH v3 08/16] " mark gross
2019-05-29 20:36 ` [RFC PATCH v3 09/16] sched: Introduce sched_class::pick_task() Vineeth Remanan Pillai
2019-08-26 17:14   ` mark gross
2019-05-29 20:36 ` [RFC PATCH v3 10/16] sched: Core-wide rq->lock Vineeth Remanan Pillai
2019-05-31 11:08   ` Peter Zijlstra
2019-05-31 15:23     ` Vineeth Pillai
2019-05-29 20:36 ` [RFC PATCH v3 11/16] sched: Basic tracking of matching tasks Vineeth Remanan Pillai
2019-08-26 20:59   ` mark gross
2019-05-29 20:36 ` [RFC PATCH v3 12/16] sched: A quick and dirty cgroup tagging interface Vineeth Remanan Pillai
2019-05-29 20:36 ` [RFC PATCH v3 13/16] sched: Add core wide task selection and scheduling Vineeth Remanan Pillai
2019-06-07 23:36   ` Pawan Gupta
2019-05-29 20:36 ` [RFC PATCH v3 14/16] sched/fair: Add a few assertions Vineeth Remanan Pillai
2019-05-29 20:36 ` [RFC PATCH v3 15/16] sched: Trivial forced-newidle balancer Vineeth Remanan Pillai
2019-05-29 20:36 ` [RFC PATCH v3 16/16] sched: Debug bits Vineeth Remanan Pillai
2019-05-29 21:02   ` Peter Oskolkov
2019-05-30 14:04 ` [RFC PATCH v3 00/16] Core scheduling v3 Aubrey Li
2019-05-30 14:17   ` Julien Desfossez
2019-05-31  4:55     ` Aubrey Li
2019-05-31  3:01   ` Aaron Lu
2019-05-31  5:12     ` Aubrey Li
2019-05-31  6:09       ` Aaron Lu
2019-05-31  6:53         ` Aubrey Li
2019-05-31  7:44           ` Aaron Lu
2019-05-31  8:26             ` Aubrey Li
2019-05-31 21:08     ` Julien Desfossez
2019-06-06 15:26       ` Julien Desfossez
2019-06-12  1:52         ` Li, Aubrey
2019-06-12 16:06           ` Julien Desfossez
2019-06-12 16:33         ` Julien Desfossez
2019-06-13  0:03           ` Subhra Mazumdar
2019-06-13  3:22             ` Julien Desfossez
2019-06-17  2:51               ` Aubrey Li
2019-06-19 18:33                 ` Julien Desfossez
2019-07-18 10:07                   ` Aaron Lu
2019-07-18 23:27                     ` Tim Chen
2019-07-19  5:52                       ` Aaron Lu
2019-07-19 11:48                         ` Aubrey Li
2019-07-19 18:33                         ` Tim Chen
2019-07-22 10:26                     ` Aubrey Li
2019-07-22 10:43                       ` Aaron Lu
2019-07-23  2:52                         ` Aubrey Li
2019-07-25 14:30                       ` Aaron Lu
2019-07-25 14:31                         ` [RFC PATCH 1/3] wrapper for cfs_rq->min_vruntime Aaron Lu
2019-07-25 14:32                         ` [PATCH 2/3] core vruntime comparison Aaron Lu
2019-08-06 14:17                           ` Peter Zijlstra
2019-07-25 14:33                         ` [PATCH 3/3] temp hack to make tick based schedule happen Aaron Lu
2019-07-25 21:42                         ` [RFC PATCH v3 00/16] Core scheduling v3 Li, Aubrey
2019-07-26 15:21                         ` Julien Desfossez
2019-07-26 21:29                           ` Tim Chen
2019-07-31  2:42                           ` Li, Aubrey
2019-08-02 15:37                             ` Julien Desfossez
2019-08-05 15:55                               ` Tim Chen
2019-08-06  3:24                                 ` Aaron Lu
2019-08-06  6:56                                   ` Aubrey Li
2019-08-06  7:04                                     ` Aaron Lu
2019-08-06 12:24                                       ` Vineeth Remanan Pillai
2019-08-06 13:49                                         ` Aaron Lu
2019-08-06 16:14                                           ` Vineeth Remanan Pillai
2019-08-06 14:16                                         ` Peter Zijlstra
2019-08-06 15:53                                           ` Vineeth Remanan Pillai
2019-08-06 17:03                                   ` Tim Chen
2019-08-06 17:12                                     ` Peter Zijlstra
2019-08-06 21:19                                       ` Tim Chen
2019-08-08  6:47                                         ` Aaron Lu
2019-08-08 17:27                                           ` Tim Chen
2019-08-08 21:42                                             ` Tim Chen
2019-08-10 14:15                                               ` Aaron Lu [this message]
2019-08-12 15:38                                                 ` Vineeth Remanan Pillai
2019-08-13  2:24                                                   ` Aaron Lu
2019-08-08 12:55                                 ` Aaron Lu
2019-08-08 16:39                                   ` Tim Chen
2019-08-10 14:18                                     ` Aaron Lu
2019-08-05 20:09                               ` Phil Auld
2019-08-06 13:54                                 ` Aaron Lu
2019-08-06 14:17                                   ` Phil Auld
2019-08-06 14:41                                     ` Aaron Lu
2019-08-06 14:55                                       ` Phil Auld
2019-08-07  8:58                               ` Dario Faggioli
2019-08-07 17:10                                 ` Tim Chen
2019-08-15 16:09                                   ` Dario Faggioli
2019-08-16  2:33                                     ` Aaron Lu
2019-09-05  1:44                                   ` Julien Desfossez
2019-09-06 22:17                                     ` Tim Chen
2019-09-18 21:27                                     ` Tim Chen
2019-09-06 18:30                                   ` Tim Chen
2019-09-11 14:02                                     ` Aaron Lu
2019-09-11 16:19                                       ` Tim Chen
2019-09-11 16:47                                         ` Vineeth Remanan Pillai
2019-09-12 12:35                                           ` Aaron Lu
2019-09-12 17:29                                             ` Tim Chen
2019-09-13 14:15                                               ` Aaron Lu
2019-09-13 17:13                                                 ` Tim Chen
2019-09-30 11:53                                             ` Vineeth Remanan Pillai
2019-10-02 20:48                                               ` Vineeth Remanan Pillai
2019-10-10 13:54                                                 ` Aaron Lu
2019-10-10 14:29                                                   ` Vineeth Remanan Pillai
2019-10-11  7:33                                                     ` Aaron Lu
2019-10-11 11:32                                                       ` Vineeth Remanan Pillai
2019-10-11 12:01                                                         ` Aaron Lu
2019-10-11 12:10                                                           ` Vineeth Remanan Pillai
2019-10-12  3:55                                                             ` Aaron Lu
2019-10-13 12:44                                                               ` Vineeth Remanan Pillai
2019-10-14  9:57                                                                 ` Aaron Lu
2019-10-21 12:30                                                                   ` Vineeth Remanan Pillai
2019-09-12 12:04                                         ` Aaron Lu
2019-09-12 17:05                                           ` Tim Chen
2019-09-13 13:57                                             ` Aaron Lu
2019-09-12 23:12                                           ` Aubrey Li
2019-09-15 14:14                                             ` Aaron Lu
2019-09-18  1:33                                               ` Aubrey Li
2019-09-18 20:40                                                 ` Tim Chen
2019-09-18 22:16                                                   ` Aubrey Li
2019-09-30 14:36                                                     ` Vineeth Remanan Pillai
2019-10-29 20:40                                                   ` Julien Desfossez
2019-11-01 21:42                                                     ` Tim Chen
2019-10-29  9:11                                               ` Dario Faggioli
2019-10-29  9:15                                                 ` Dario Faggioli
2019-10-29  9:16                                                 ` Dario Faggioli
2019-10-29  9:17                                                 ` Dario Faggioli
2019-10-29  9:18                                                 ` Dario Faggioli
2019-10-29  9:18                                                 ` Dario Faggioli
2019-10-29  9:19                                                 ` Dario Faggioli
2019-10-29  9:20                                                 ` Dario Faggioli
2019-10-29 20:34                                                   ` Julien Desfossez
2019-11-15 16:30                                                     ` Dario Faggioli
2019-09-25  2:40                                     ` Aubrey Li
2019-09-25 17:24                                       ` Tim Chen
2019-09-25 22:07                                         ` Aubrey Li
2019-09-30 15:22                                     ` Julien Desfossez
2019-08-27 21:14 ` Matthew Garrett
2019-08-27 21:50   ` Peter Zijlstra
2019-08-28 15:30     ` Phil Auld
2019-08-28 16:01       ` Peter Zijlstra
2019-08-28 16:37         ` Tim Chen
2019-08-29 14:30         ` Phil Auld
2019-08-29 14:38           ` Peter Zijlstra
2019-09-10 14:27             ` Julien Desfossez
2019-09-18 21:12               ` Tim Chen
2019-08-28 15:59     ` Tim Chen
2019-08-28 16:16       ` Peter Zijlstra
2019-08-27 23:24   ` Aubrey Li

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