From: Morten Rasmussen <morten.rasmussen@arm.com>
To: peterz@infradead.org, mingo@redhat.com
Cc: dietmar.eggemann@arm.com, yuyang.du@intel.com,
vincent.guittot@linaro.org, mgalbraith@suse.de,
linux-kernel@vger.kernel.org,
Morten Rasmussen <morten.rasmussen@arm.com>
Subject: [PATCH v2 11/13] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups
Date: Wed, 22 Jun 2016 18:03:22 +0100 [thread overview]
Message-ID: <1466615004-3503-12-git-send-email-morten.rasmussen@arm.com> (raw)
In-Reply-To: <1466615004-3503-1-git-send-email-morten.rasmussen@arm.com>
For asymmetric cpu capacity systems it is counter-productive for
throughput if low capacity cpus are pulling tasks from non-overloaded
cpus with higher capacity. The assumption is that higher cpu capacity is
preferred over running alone in a group with lower cpu capacity.
This patch rejects higher cpu capacity groups with one or less task per
cpu as potential busiest group which could otherwise lead to a series of
failing load-balancing attempts leading to a force-migration.
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
---
kernel/sched/fair.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4d10d022006d..ca0048d95b3f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6789,6 +6789,17 @@ group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
return false;
}
+/*
+ * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
+ * per-cpu capacity than sched_group ref.
+ */
+static inline bool
+group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
+{
+ return sg->sgc->max_capacity * capacity_margin <
+ ref->sgc->max_capacity * 1024;
+}
+
static inline enum
group_type group_classify(struct sched_group *group,
struct sg_lb_stats *sgs)
@@ -6892,6 +6903,19 @@ static bool update_sd_pick_busiest(struct lb_env *env,
if (sgs->avg_load <= busiest->avg_load)
return false;
+ if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
+ goto asym_packing;
+
+ /* Candidate sg has no more than one task per cpu and has
+ * higher per-cpu capacity. Migrating tasks to less capable
+ * cpus may harm throughput. Maximize throughput,
+ * power/energy consequences are not considered.
+ */
+ if (sgs->sum_nr_running <= sgs->group_weight &&
+ group_smaller_cpu_capacity(sds->local, sg))
+ return false;
+
+asym_packing:
/* This is the busiest node in its class. */
if (!(env->sd->flags & SD_ASYM_PACKING))
return true;
--
1.9.1
next prev parent reply other threads:[~2016-06-22 17:02 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-22 17:03 [PATCH v2 00/13] sched: Clean-ups and asymmetric cpu capacity support Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 01/13] sched: Fix power to capacity renaming in comment Morten Rasmussen
2016-08-10 18:03 ` [tip:sched/core] sched/core: " tip-bot for Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 02/13] sched/fair: Consistent use of prev_cpu in wakeup path Morten Rasmussen
2016-06-22 18:04 ` Rik van Riel
2016-06-23 9:56 ` Morten Rasmussen
2016-06-23 12:24 ` Rik van Riel
2016-08-10 18:03 ` [tip:sched/core] sched/fair: Make the use of prev_cpu consistent in the " tip-bot for Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 03/13] sched/fair: Optimize find_idlest_cpu() when there is no choice Morten Rasmussen
2016-07-13 12:20 ` Vincent Guittot
2016-08-10 18:03 ` [tip:sched/core] " tip-bot for Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 04/13] sched: Introduce SD_ASYM_CPUCAPACITY sched_domain topology flag Morten Rasmussen
2016-07-11 9:55 ` Peter Zijlstra
2016-07-11 10:42 ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 05/13] sched: Enable SD_BALANCE_WAKE for asymmetric capacity systems Morten Rasmussen
2016-07-11 10:04 ` Peter Zijlstra
2016-07-11 10:37 ` Morten Rasmussen
2016-07-11 11:04 ` Morten Rasmussen
2016-07-11 11:24 ` Peter Zijlstra
2016-07-12 14:26 ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 06/13] sched: Store maximum per-cpu capacity in root domain Morten Rasmussen
2016-07-11 10:18 ` Peter Zijlstra
2016-07-11 16:16 ` Dietmar Eggemann
2016-07-12 11:42 ` Peter Zijlstra
2016-07-13 11:18 ` Dietmar Eggemann
2016-07-13 12:40 ` Vincent Guittot
2016-07-13 13:48 ` Dietmar Eggemann
2016-07-13 16:37 ` Morten Rasmussen
2016-07-14 13:25 ` Vincent Guittot
2016-07-14 15:15 ` Morten Rasmussen
2016-07-15 11:46 ` Morten Rasmussen
2016-07-15 13:39 ` Vincent Guittot
2016-07-15 16:02 ` Morten Rasmussen
2016-07-18 12:48 ` Vincent Guittot
2016-07-18 15:11 ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 07/13] sched/fair: Let asymmetric cpu configurations balance at wake-up Morten Rasmussen
2016-07-11 11:13 ` Peter Zijlstra
2016-07-11 12:32 ` Morten Rasmussen
2016-07-13 12:56 ` Vincent Guittot
2016-07-13 16:14 ` Morten Rasmussen
2016-07-14 13:45 ` Vincent Guittot
2016-07-15 8:37 ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 08/13] sched/fair: Compute task/cpu utilization at wake-up more correctly Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 09/13] sched/fair: Consider spare capacity in find_idlest_group() Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 10/13] sched: Add per-cpu max capacity to sched_group_capacity Morten Rasmussen
2016-06-22 17:03 ` Morten Rasmussen [this message]
2016-06-23 21:20 ` [PATCH v2 11/13] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups Sai Gurrappadi
2016-06-30 7:49 ` Morten Rasmussen
2016-07-14 16:39 ` Sai Gurrappadi
2016-07-15 8:39 ` Morten Rasmussen
2016-07-12 12:59 ` Peter Zijlstra
2016-07-12 14:34 ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 12/13] arm: Set SD_ASYM_CPUCAPACITY for big.LITTLE platforms Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 13/13] arm: Update arch_scale_cpu_capacity() to reflect change to define Morten Rasmussen
2016-06-28 10:20 ` [PATCH v2 00/13] sched: Clean-ups and asymmetric cpu capacity support Koan-Sin Tan
2016-06-30 7:53 ` Morten Rasmussen
2016-07-08 7:35 ` KEITA KOBAYASHI
2016-07-08 8:18 ` Morten Rasmussen
2016-07-11 8:33 ` Morten Rasmussen
2016-07-11 12:44 ` Vincent Guittot
2016-07-12 13:25 ` Peter Zijlstra
2016-07-12 14:39 ` Morten Rasmussen
2016-07-13 12:06 ` Vincent Guittot
2016-07-13 15:54 ` Morten Rasmussen
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=1466615004-3503-12-git-send-email-morten.rasmussen@arm.com \
--to=morten.rasmussen@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgalbraith@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=vincent.guittot@linaro.org \
--cc=yuyang.du@intel.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).