From: tip-bot for Mike Galbraith <bitbucket@online.de>
To: linux-tip-commits@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org,
a.p.zijlstra@chello.nl, bitbucket@online.de, tglx@linutronix.de
Subject: [tip:sched/core] sched: Fix select_idle_sibling() bouncing cow syndrome
Date: Mon, 4 Feb 2013 11:25:53 -0800 [thread overview]
Message-ID: <tip-e0a79f529d5ba2507486d498b25da40911d95cf6@git.kernel.org> (raw)
In-Reply-To: <1359371965.5783.127.camel@marge.simpson.net>
Commit-ID: e0a79f529d5ba2507486d498b25da40911d95cf6
Gitweb: http://git.kernel.org/tip/e0a79f529d5ba2507486d498b25da40911d95cf6
Author: Mike Galbraith <bitbucket@online.de>
AuthorDate: Mon, 28 Jan 2013 12:19:25 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 4 Feb 2013 20:07:24 +0100
sched: Fix select_idle_sibling() bouncing cow syndrome
If the previous CPU is cache affine and idle, select it.
The current implementation simply traverses the sd_llc domain,
taking the first idle CPU encountered, which walks buddy pairs
hand in hand over the package, inflicting excruciating pain.
1 tbench pair (worst case) in a 10 core + SMT package:
pre 15.22 MB/sec 1 procs
post 252.01 MB/sec 1 procs
Signed-off-by: Mike Galbraith <bitbucket@online.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1359371965.5783.127.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/fair.c | 21 +++++++--------------
1 file changed, 7 insertions(+), 14 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8dbee9f..ed18c74 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3252,25 +3252,18 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
*/
static int select_idle_sibling(struct task_struct *p, int target)
{
- int cpu = smp_processor_id();
- int prev_cpu = task_cpu(p);
struct sched_domain *sd;
struct sched_group *sg;
- int i;
+ int i = task_cpu(p);
- /*
- * If the task is going to be woken-up on this cpu and if it is
- * already idle, then it is the right target.
- */
- if (target == cpu && idle_cpu(cpu))
- return cpu;
+ if (idle_cpu(target))
+ return target;
/*
- * If the task is going to be woken-up on the cpu where it previously
- * ran and if it is currently idle, then it the right target.
+ * If the prevous cpu is cache affine and idle, don't be stupid.
*/
- if (target == prev_cpu && idle_cpu(prev_cpu))
- return prev_cpu;
+ if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
+ return i;
/*
* Otherwise, iterate the domains and find an elegible idle cpu.
@@ -3284,7 +3277,7 @@ static int select_idle_sibling(struct task_struct *p, int target)
goto next;
for_each_cpu(i, sched_group_cpus(sg)) {
- if (!idle_cpu(i))
+ if (i == target || !idle_cpu(i))
goto next;
}
prev parent reply other threads:[~2013-02-04 19:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-27 7:50 [patch] sched: minimalist select_idle_sibling() bouncing cow syndrome fix Mike Galbraith
2013-01-28 10:53 ` Ingo Molnar
2013-01-28 11:19 ` Mike Galbraith
2013-01-28 11:21 ` Ingo Molnar
2013-01-28 11:28 ` Mike Galbraith
2013-02-04 19:25 ` tip-bot for Mike Galbraith [this message]
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=tip-e0a79f529d5ba2507486d498b25da40911d95cf6@git.kernel.org \
--to=bitbucket@online.de \
--cc=a.p.zijlstra@chello.nl \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=tglx@linutronix.de \
/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).