From: Julien Desfossez <jdesfossez@digitalocean.com>
To: Aaron Lu <aaron.lu@linux.alibaba.com>
Cc: "Aubrey Li" <aubrey.intel@gmail.com>,
"Vineeth Remanan Pillai" <vpillai@digitalocean.com>,
"Nishanth Aravamudan" <naravamudan@digitalocean.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Tim Chen" <tim.c.chen@linux.intel.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>,
"Subhra Mazumdar" <subhra.mazumdar@oracle.com>,
"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, 12 Jun 2019 12:33:45 -0400 [thread overview]
Message-ID: <20190612163345.GB26997@sinkpad> (raw)
In-Reply-To: <20190606152637.GA5703@sinkpad>
After reading more traces and trying to understand why only untagged
tasks are starving when there are cpu-intensive tasks running on the
same set of CPUs, we noticed a difference in behavior in ‘pick_task’. In
the case where ‘core_cookie’ is 0, we are supposed to only prefer the
tagged task if it’s priority is higher, but when the priorities are
equal we prefer it as well which causes the starving. ‘pick_task’ is
biased toward selecting its first parameter in case of equality which in
this case was the ‘class_pick’ instead of ‘max’. Reversing the order of
the parameter solves this issue and matches the expected behavior.
So we can get rid of this vruntime_boost concept.
We have tested the fix below and it seems to work well with
tagged/untagged tasks.
Here are our initial test results. When core scheduling is enabled,
each VM (and associated vhost threads) are in their own cgroup/tag.
1 12-vcpu VM MySQL TPC-C benchmark (IO + CPU) with 96 mostly-idle 1-vcpu
VMs on each NUMA node (72 logical CPUs total with SMT on):
+-------------+----------+--------------+------------+--------+
| | baseline | coresched | coresched | nosmt |
| | no tag | VMs tagged | VMs tagged | no tag |
| | v5.1.5 | no stall fix | stall fix | |
+-------------+----------+--------------+------------+--------+
|average TPS | 1474 | 1289 | 1264 | 1339 |
|stdev | 48 | 12 | 17 | 24 |
|overhead | N/A | -12% | -14% | -9% |
+-------------+----------+--------------+------------+--------+
3 12-vcpu VMs running linpack (cpu-intensive), all pinned on the same
NUMA node (36 logical CPUs with SMT enabled on that NUMA node):
+---------------+----------+--------------+-----------+--------+
| | baseline | coresched | coresched | nosmt |
| | no tag | VMs tagged | VMs tagged| no tag |
| | v5.1.5 | no stall fix | stall fix | |
+---------------+----------+--------------+-----------+--------+
|average gflops | 177.9 | 171.3 | 172.7 | 81.9 |
|stdev | 2.6 | 10.6 | 6.4 | 8.1 |
|overhead | N/A | -3.7% | -2.9% | -53.9% |
+---------------+----------+--------------+-----------+--------+
This fix can be toggled dynamically with the ‘CORESCHED_STALL_FIX’
sched_feature so it’s easy to test before/after (it is disabled by
default).
The up-to-date git tree can also be found here in case it’s easier to
follow:
https://github.com/digitalocean/linux-coresched/commits/vpillai/coresched-v3-v5.1.5-test
Feedback welcome !
Thanks,
Julien
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6e79421..26fea68 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3668,8 +3668,10 @@ pick_task(struct rq *rq, const struct sched_class *class, struct task_struct *ma
* 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))
+ bool max_is_higher = sched_feat(CORESCHED_STALL_FIX) ?
+ max && !prio_less(max, class_pick) :
+ max && prio_less(class_pick, max);
+ if (class_pick->core_cookie && max_is_higher)
return idle_sched_class.pick_task(rq);
return class_pick;
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 858589b..332a092 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -90,3 +90,9 @@ SCHED_FEAT(WA_BIAS, true)
* UtilEstimation. Use estimated CPU utilization.
*/
SCHED_FEAT(UTIL_EST, true)
+
+/*
+ * Prevent task stall due to vruntime comparison limitation across
+ * cpus.
+ */
+SCHED_FEAT(CORESCHED_STALL_FIX, false)
next prev parent reply other threads:[~2019-06-12 16:33 UTC|newest]
Thread overview: 161+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-29 20:36 [RFC PATCH v3 00/16] Core scheduling v3 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 [this message]
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
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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