From: Uladzislau Rezki <urezki@gmail.com>
To: Ingo Molnar <mingo@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Uladzislau 2 Rezki <uladzislau2.rezki@sonymobile.com>
Subject: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE
Date: Wed, 8 Feb 2017 09:43:29 +0100 [thread overview]
Message-ID: <1486543409-11493-3-git-send-email-urezki@gmail.com> (raw)
In-Reply-To: <1486543409-11493-1-git-send-email-urezki@gmail.com>
From: Uladzislau 2 Rezki <uladzislau2.rezki@sonymobile.com>
A load balancer calculates imbalance factor for particular shed
domain and tries to steal up the prescribed amount of weighted load.
However, a small imbalance factor would sometimes prevent us from
stealing any tasks at all. When a CPU is newly idle, it should
steal first task which passes a migration criteria.
Signed-off-by: Uladzislau 2 Rezki <uladzislau2.rezki@sonymobile.com>
---
kernel/sched/fair.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 232ef3c..29e0d7f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6802,6 +6802,14 @@ static int detach_tasks(struct lb_env *env)
if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
break;
+ /*
+ * Another CPU can place tasks, since we do not hold dst_rq lock
+ * while doing balancing. If newly idle CPU already got something,
+ * give up to reduce latency.
+ */
+ if (env->idle == CPU_NEWLY_IDLE && env->dst_rq->nr_running > 0)
+ break;
+
p = list_first_entry(tasks, struct task_struct, se.group_node);
env->loop++;
@@ -6824,8 +6832,9 @@ static int detach_tasks(struct lb_env *env)
if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
goto next;
- if ((load / 2) > env->imbalance)
- goto next;
+ if (env->idle != CPU_NEWLY_IDLE)
+ if ((load / 2) > env->imbalance)
+ goto next;
detach_task(p, env);
list_add(&p->se.group_node, &env->tasks);
--
2.1.4
next prev parent reply other threads:[~2017-02-08 8:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-08 8:43 [RFC,v2 1/3] sched: set loop_max after rq lock is taken Uladzislau Rezki
2017-02-08 8:43 ` [RFC,v2 2/3] sched: set number of iterations to h_nr_running Uladzislau Rezki
2017-02-09 12:20 ` Peter Zijlstra
2017-02-09 18:59 ` Uladzislau Rezki
2017-02-08 8:43 ` Uladzislau Rezki [this message]
2017-02-08 9:19 ` [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE Mike Galbraith
2017-02-09 10:12 ` Uladzislau Rezki
2017-02-09 12:22 ` Peter Zijlstra
2017-02-09 18:54 ` Uladzislau Rezki
2017-02-13 13:51 ` Peter Zijlstra
2017-02-13 17:17 ` Uladzislau Rezki
2017-02-14 18:28 ` Uladzislau Rezki
2017-02-15 18:58 ` Dietmar Eggemann
2017-02-16 11:20 ` Uladzislau Rezki
2017-03-08 15:35 ` Uladzislau Rezki
2017-02-09 12:14 ` [RFC,v2 1/3] sched: set loop_max after rq lock is taken Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1486543409-11493-3-git-send-email-urezki@gmail.com \
--to=urezki@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=uladzislau2.rezki@sonymobile.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).