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From: Vineeth Remanan Pillai <vpillai@digitalocean.com>
To: Aaron Lu <aaron.lu@linux.alibaba.com>
Cc: "Tim Chen" <tim.c.chen@linux.intel.com>,
	"Julien Desfossez" <jdesfossez@digitalocean.com>,
	"Dario Faggioli" <dfaggioli@suse.com>,
	"Li, Aubrey" <aubrey.li@linux.intel.com>,
	"Aubrey Li" <aubrey.intel@gmail.com>,
	"Nishanth Aravamudan" <naravamudan@digitalocean.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"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: Wed, 2 Oct 2019 16:48:14 -0400	[thread overview]
Message-ID: <CANaguZDOb+rVcDPMS+SR1DKc73fnctkBK0EbfBrf90dztr8t=Q@mail.gmail.com> (raw)
In-Reply-To: <CANaguZBTiLQiRQU9MJR2Qys8S2S=-PTe66_ZPi5DVzpPbJ93zw@mail.gmail.com>

On Mon, Sep 30, 2019 at 7:53 AM Vineeth Remanan Pillai
<vpillai@digitalocean.com> wrote:
>
> >
> Sorry, I misunderstood the fix and I did not initially see the core wide
> min_vruntime that you tried to maintain in the rq->core. This approach
> seems reasonable. I think we can fix the potential starvation that you
> mentioned in the comment by adjusting for the difference in all the children
> cfs_rq when we set the minvruntime in rq->core. Since we take the lock for
> both the queues, it should be doable and I am trying to see how we can best
> do that.
>
Attaching here with, the 2 patches I was working on in preparation of v4.

Patch 1 is an improvement of patch 2 of Aaron where I am propagating the
vruntime changes to the whole tree.
Patch 2 is an improvement for patch 3 of Aaron where we do resched_curr
only when the sibling is forced idle.

Micro benchmarks seems good. Will be doing larger set of tests and hopefully
posting v4 by end of week. Please let me know what you think of these patches
(patch 1 is on top of Aaron's patch 2, patch 2 replaces Aaron's patch 3)

Thanks,
Vineeth

[PATCH 1/2] sched/fair: propagate the min_vruntime change to the whole rq tree

When we adjust the min_vruntime of rq->core, we need to propgate
that down the tree so as to not cause starvation of existing tasks
based on previous vruntime.
---
 kernel/sched/fair.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 59cb01a1563b..e8dd78a8c54d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -476,6 +476,23 @@ static inline u64 cfs_rq_min_vruntime(struct
cfs_rq *cfs_rq)
                return cfs_rq->min_vruntime;
 }

+static void coresched_adjust_vruntime(struct cfs_rq *cfs_rq, u64 delta)
+{
+       struct sched_entity *se, *next;
+
+       if (!cfs_rq)
+               return;
+
+       cfs_rq->min_vruntime -= delta;
+       rbtree_postorder_for_each_entry_safe(se, next,
+                       &cfs_rq->tasks_timeline.rb_root, run_node) {
+               if (se->vruntime > delta)
+                       se->vruntime -= delta;
+               if (se->my_q)
+                       coresched_adjust_vruntime(se->my_q, delta);
+       }
+}
+
 static void update_core_cfs_rq_min_vruntime(struct cfs_rq *cfs_rq)
 {
        struct cfs_rq *cfs_rq_core;
@@ -487,8 +504,11 @@ static void
update_core_cfs_rq_min_vruntime(struct cfs_rq *cfs_rq)
                return;

        cfs_rq_core = core_cfs_rq(cfs_rq);
-       cfs_rq_core->min_vruntime = max(cfs_rq_core->min_vruntime,
-                                       cfs_rq->min_vruntime);
+       if (cfs_rq_core != cfs_rq &&
+           cfs_rq->min_vruntime < cfs_rq_core->min_vruntime) {
+               u64 delta = cfs_rq_core->min_vruntime - cfs_rq->min_vruntime;
+               coresched_adjust_vruntime(cfs_rq_core, delta);
+       }
 }

 bool cfs_prio_less(struct task_struct *a, struct task_struct *b)
--
2.17.1

[PATCH 2/2] sched/fair : Wake up forced idle siblings if needed

If a cpu has only one task and if it has used up its timeslice,
then we should try to wake up the sibling to give the forced idle
thread a chance.
We do that by triggering schedule which will IPI the sibling if
the task in the sibling wins the priority check.
---
 kernel/sched/fair.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e8dd78a8c54d..ba4d929abae6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4165,6 +4165,13 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct
sched_entity *se, int flags)
                update_min_vruntime(cfs_rq);
 }

+static inline bool
+__entity_slice_used(struct sched_entity *se)
+{
+       return (se->sum_exec_runtime - se->prev_sum_exec_runtime) >
+               sched_slice(cfs_rq_of(se), se);
+}
+
 /*
  * Preempt the current task with a newly woken task if needed:
  */
@@ -10052,6 +10059,39 @@ static void rq_offline_fair(struct rq *rq)

 #endif /* CONFIG_SMP */

+#ifdef CONFIG_SCHED_CORE
+/*
+ * If runqueue has only one task which used up its slice and
+ * if the sibling is forced idle, then trigger schedule
+ * to give forced idle task a chance.
+ */
+static void resched_forceidle(struct rq *rq, struct sched_entity *se)
+{
+       int cpu = cpu_of(rq), sibling_cpu;
+       if (rq->cfs.nr_running > 1 || !__entity_slice_used(se))
+               return;
+
+       for_each_cpu(sibling_cpu, cpu_smt_mask(cpu)) {
+               struct rq *sibling_rq;
+               if (sibling_cpu == cpu)
+                       continue;
+               if (cpu_is_offline(sibling_cpu))
+                       continue;
+
+               sibling_rq = cpu_rq(sibling_cpu);
+               if (sibling_rq->core_forceidle) {
+                       resched_curr(rq);
+                       break;
+               }
+       }
+}
+#else
+static inline void resched_forceidle(struct rq *rq, struct sched_entity *se)
+{
+}
+#endif
+
+
 /*
  * scheduler tick hitting a task of our scheduling class.
  *
@@ -10075,6 +10115,9 @@ static void task_tick_fair(struct rq *rq,
struct task_struct *curr, int queued)

        update_misfit_status(curr, rq);
        update_overutilized_status(task_rq(curr));
+
+       if (sched_core_enabled(rq))
+               resched_forceidle(rq, &curr->se);
 }

 /*
--
2.17.1

  reply	other threads:[~2019-10-02 20:48 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
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 [this message]
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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