linux-kernel - [tip:sched/core] sched/fair: Let asymmetric CPU configurations balance at wake-up

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-3273163c6775c4c21823985304c2364b08ca6ea2@git.kernel.org>
Date:	Thu, 18 Aug 2016 03:58:42 -0700
From:	tip-bot for Morten Rasmussen <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, mingo@...nel.org, vincent.guittot@...aro.org,
	tglx@...utronix.de, peterz@...radead.org,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	morten.rasmussen@....com, efault@....de
Subject: [tip:sched/core] sched/fair: Let asymmetric CPU configurations
 balance at wake-up

Commit-ID:  3273163c6775c4c21823985304c2364b08ca6ea2
Gitweb:     http://git.kernel.org/tip/3273163c6775c4c21823985304c2364b08ca6ea2
Author:     Morten Rasmussen <morten.rasmussen@....com>
AuthorDate: Mon, 25 Jul 2016 14:34:26 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 18 Aug 2016 11:26:56 +0200

sched/fair: Let asymmetric CPU configurations balance at wake-up

Currently, SD_WAKE_AFFINE always takes priority over wakeup balancing if
SD_BALANCE_WAKE is set on the sched_domains. For asymmetric
configurations SD_WAKE_AFFINE is only desirable if the waking task's
compute demand (utilization) is suitable for the waking CPU and the
previous CPU, and all CPUs within their respective
SD_SHARE_PKG_RESOURCES domains (sd_llc). If not, let wakeup balancing
take over (find_idlest_{group, cpu}()).

This patch makes affine wake-ups conditional on whether both the waker
CPU and the previous CPU has sufficient capacity for the waking task,
or not, assuming that the CPU capacities within an SD_SHARE_PKG_RESOURCES
domain (sd_llc) are homogeneous.

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: dietmar.eggemann@....com
Cc: freedom.tan@...iatek.com
Cc: keita.kobayashi.ym@...esas.com
Cc: mgalbraith@...e.de
Cc: sgurrappadi@...dia.com
Cc: yuyang.du@...el.com
Link: http://lkml.kernel.org/r/1469453670-2660-10-git-send-email-morten.rasmussen@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index acdc351..61d4854 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -114,6 +114,12 @@ unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
 #endif
 
+/*
+ * The margin used when comparing utilization with CPU capacity:
+ * util * 1024 < capacity * margin
+ */
+unsigned int capacity_margin = 1280; /* ~20% */
+
 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
 {
 	lw->weight += inc;
@@ -5376,6 +5382,32 @@ static int cpu_util(int cpu)
 	return (util >= capacity) ? capacity : util;
 }
 
+static inline int task_util(struct task_struct *p)
+{
+	return p->se.avg.util_avg;
+}
+
+/*
+ * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
+ * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
+ *
+ * In that case WAKE_AFFINE doesn't make sense and we'll let
+ * BALANCE_WAKE sort things out.
+ */
+static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
+{
+	long min_cap, max_cap;
+
+	min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
+	max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;
+
+	/* Minimum capacity is close to max, no need to abort wake_affine */
+	if (max_cap - min_cap < max_cap >> 3)
+		return 0;
+
+	return min_cap * 1024 < task_util(p) * capacity_margin;
+}
+
 /*
  * select_task_rq_fair: Select target runqueue for the waking task in domains
  * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
@@ -5399,7 +5431,8 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
 
 	if (sd_flag & SD_BALANCE_WAKE) {
 		record_wakee(p);
-		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
+		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
+			      && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
 	}
 
 	rcu_read_lock();