From: tip-bot for Frederic Weisbecker <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: paulmck@linux.vnet.ibm.com, tglx@linutronix.de,
byungchul.park@lge.com, mingo@kernel.org, efault@gmx.de,
riel@redhat.com, lcapitulino@redhat.com,
linux-kernel@vger.kernel.org, fweisbec@gmail.com,
cmetcalf@ezchip.com, hpa@zytor.com, cl@linux.com,
peterz@infradead.org
Subject: [tip:sched/core] sched/fair: Optimize !CONFIG_NO_HZ_COMMON CPU load updates
Date: Sat, 23 Apr 2016 05:59:33 -0700 [thread overview]
Message-ID: <tip-9fd81dd5ce0b12341c9f83346f8d32ac68bd3841@git.kernel.org> (raw)
In-Reply-To: <1461080211-16271-1-git-send-email-fweisbec@gmail.com>
Commit-ID: 9fd81dd5ce0b12341c9f83346f8d32ac68bd3841
Gitweb: http://git.kernel.org/tip/9fd81dd5ce0b12341c9f83346f8d32ac68bd3841
Author: Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Tue, 19 Apr 2016 17:36:51 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 23 Apr 2016 14:20:42 +0200
sched/fair: Optimize !CONFIG_NO_HZ_COMMON CPU load updates
Some code in CPU load update only concern NO_HZ configs but it is
built on all configurations. When NO_HZ isn't built, that code is harmless
but just happens to take some useless ressources in CPU and memory:
1) one useless field in struct rq
2) jiffies record on every tick that is never used (cpu_load_update_periodic)
3) decay_load_missed is called two times on every tick to eventually
return immediately with no action taken. And that function is dead
code.
For pure optimization purposes, lets conditionally build the NO_HZ
related code.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1461080211-16271-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/core.c | 5 ++---
kernel/sched/fair.c | 9 +++++++--
kernel/sched/sched.h | 6 ++++--
3 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c98a268..71dffbb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7381,8 +7381,6 @@ void __init sched_init(void)
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
rq->cpu_load[j] = 0;
- rq->last_load_update_tick = jiffies;
-
#ifdef CONFIG_SMP
rq->sd = NULL;
rq->rd = NULL;
@@ -7401,12 +7399,13 @@ void __init sched_init(void)
rq_attach_root(rq, &def_root_domain);
#ifdef CONFIG_NO_HZ_COMMON
+ rq->last_load_update_tick = jiffies;
rq->nohz_flags = 0;
#endif
#ifdef CONFIG_NO_HZ_FULL
rq->last_sched_tick = 0;
#endif
-#endif
+#endif /* CONFIG_SMP */
init_rq_hrtick(rq);
atomic_set(&rq->nr_iowait, 0);
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b70367a..b8a33ab 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4491,7 +4491,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
}
#ifdef CONFIG_SMP
-
+#ifdef CONFIG_NO_HZ_COMMON
/*
* per rq 'load' arrray crap; XXX kill this.
*/
@@ -4557,6 +4557,7 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
}
return load;
}
+#endif /* CONFIG_NO_HZ_COMMON */
/**
* __cpu_load_update - update the rq->cpu_load[] statistics
@@ -4596,7 +4597,7 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
unsigned long pending_updates)
{
- unsigned long tickless_load = this_rq->cpu_load[0];
+ unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
int i, scale;
this_rq->nr_load_updates++;
@@ -4609,6 +4610,7 @@ static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
/* scale is effectively 1 << i now, and >> i divides by scale */
old_load = this_rq->cpu_load[i];
+#ifdef CONFIG_NO_HZ_COMMON
old_load = decay_load_missed(old_load, pending_updates - 1, i);
if (tickless_load) {
old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
@@ -4619,6 +4621,7 @@ static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
*/
old_load += tickless_load;
}
+#endif
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This
@@ -4731,8 +4734,10 @@ static inline void cpu_load_update_nohz(struct rq *this_rq,
static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
+#ifdef CONFIG_NO_HZ_COMMON
/* See the mess around cpu_load_update_nohz(). */
this_rq->last_load_update_tick = READ_ONCE(jiffies);
+#endif
cpu_load_update(this_rq, load, 1);
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 32d9e22..69da6fc 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -585,11 +585,13 @@ struct rq {
#endif
#define CPU_LOAD_IDX_MAX 5
unsigned long cpu_load[CPU_LOAD_IDX_MAX];
- unsigned long last_load_update_tick;
#ifdef CONFIG_NO_HZ_COMMON
+#ifdef CONFIG_SMP
+ unsigned long last_load_update_tick;
+#endif /* CONFIG_SMP */
u64 nohz_stamp;
unsigned long nohz_flags;
-#endif
+#endif /* CONFIG_NO_HZ_COMMON */
#ifdef CONFIG_NO_HZ_FULL
unsigned long last_sched_tick;
#endif
prev parent reply other threads:[~2016-04-23 13:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-13 13:56 [PATCH 0/3] sched: Fix/improve nohz cpu load updates v3 Frederic Weisbecker
2016-04-13 13:56 ` [PATCH 1/3] sched: Gather cpu load functions under a more conventional namespace Frederic Weisbecker
2016-04-23 12:58 ` [tip:sched/core] sched/fair: Gather CPU " tip-bot for Frederic Weisbecker
2016-04-13 13:56 ` [PATCH 2/3] sched: Correctly handle nohz ticks cpu load accounting Frederic Weisbecker
2016-04-18 8:22 ` Byungchul Park
2016-04-18 9:17 ` Byungchul Park
2016-04-18 13:35 ` Frederic Weisbecker
2016-04-19 0:01 ` Byungchul Park
2016-04-19 14:01 ` Frederic Weisbecker
2016-04-20 7:59 ` Wanpeng Li
2016-04-23 12:59 ` [tip:sched/core] sched/fair: Correctly handle nohz ticks CPU " tip-bot for Frederic Weisbecker
2016-04-13 13:56 ` [PATCH 3/3] sched: Optimize !CONFIG_NO_HZ_COMMON cpu load updates Frederic Weisbecker
2016-04-18 13:36 ` Frederic Weisbecker
2016-04-19 15:36 ` [PATCH v2] " Frederic Weisbecker
2016-04-23 12:59 ` tip-bot for Frederic Weisbecker [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-9fd81dd5ce0b12341c9f83346f8d32ac68bd3841@git.kernel.org \
--to=tipbot@zytor.com \
--cc=byungchul.park@lge.com \
--cc=cl@linux.com \
--cc=cmetcalf@ezchip.com \
--cc=efault@gmx.de \
--cc=fweisbec@gmail.com \
--cc=hpa@zytor.com \
--cc=lcapitulino@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=riel@redhat.com \
--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).