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From 3477712d21ac713611aa74f9f5a6ff4b1e49a930 Mon Sep 17 00:00:00 2001
From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Date: Thu, 30 Jul 2015 16:53:30 +0100
Subject: [PATCH 49/92] sched: EAS & cpu hotplug interoperability
For Energy-Aware Scheduling (EAS) to work properly, even in the case that
cpus are hot-plugged out, the energy model (EM) data on all energy-aware
sched domains has to be present for all online cpus.
Mainline sd hierarchy setup code will remove sd's which are not useful for
task scheduling e.g. in the following situations:
1. Only one cpu remains in one cluster of a two cluster system.
This remaining cpu only has DIE and no MC sd.
2. A complete cluster in a two-cluster system is hot-plugged out.
The cpus of the remaining cluster only have MC and no DIE sd.
To make sure that all online cpus keep all their energy-aware sd's,
the sd degenerate functionality has been changed to not free sd's if
their first sg contains EM data in case:
1. There is only one cpu left in the sd.
2. There have to be at least 2 sg's if certain sd flags are set.
Instead of freeing such an sd it now clears only its SD_LOAD_BALANCE
flag.
This will make sure that the EAS functionality will always see all
energy-aware sd's for all online cpus.
It will introduce a (small ?) performance degradation since the
hot-path macro for_each_domain() has to deal with sd's not
contributing to task-scheduling at all now. There is the handling
of newidle decay values before the SD_LOAD_BALANCE check in
rebalance_domains().
But generally, code to make sure that task scheduling is not invoked
on these sd's is in place (if (!(sd->flags & SD_LOAD_BALANCE))
already.
This patch has been tested on a single (a7) cluster TC2 system. I.e. we
could abandon the SYS sd level patch and use this patch to solve all
problems related to sd topology setups and runtime changes.
This patch should not be squashed.
Test (w/ CONFIG_SCHED_DEBUG):
JUNO:
$ cat /proc/cpuinfo | grep "^CPU part"
CPU part : 0xd03
CPU part : 0xd07
CPU part : 0xd07
CPU part : 0xd03
CPU part : 0xd03
CPU part : 0xd03
$ cat /proc/sys/kernel/sched_domain/cpu*/domain*/{name,flags}
MC
DIE
MC
DIE
MC
DIE
MC
DIE
MC
DIE
MC
DIE
33583 - 0x832f
4143 - 0x102f
33583
4143
33583
4143
33583
4143
33583
4143
33583
4143
Hotplug-out A57 cluster
$ echo 0 > /sys/devices/system/cpu/cpu1/online
$ echo 0 > /sys/devices/system/cpu/cpu2/online
$ cat /proc/sys/kernel/sched_domain/cpu*/domain*/{name,flags}
MC
DIE
MC
DIE
MC
DIE
MC
DIE
33583
4142 - 0x102e <-- !SD_LOAD_BALANCE
33583
4142
33583
4142
33583
4142
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
(cherry picked from commit a5ebdd0fe5357fe125d9603d766adc69e7607981)
Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
---
kernel/sched/core.c | 17 ++++++++++-------
kernel/sched/fair.c | 7 +++++--
2 files changed, 15 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 083b318..f31ea62 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5663,9 +5663,6 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
if (!(sd->flags & SD_LOAD_BALANCE)) {
printk("does not load-balance\n");
- if (sd->parent)
- printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
- " has parent");
return -1;
}
@@ -5760,8 +5757,12 @@ static inline bool sched_debug(void)
static int sd_degenerate(struct sched_domain *sd)
{
- if (cpumask_weight(sched_domain_span(sd)) == 1)
- return 1;
+ if (cpumask_weight(sched_domain_span(sd)) == 1) {
+ if (sd->groups->sge)
+ sd->flags &= ~SD_LOAD_BALANCE;
+ else
+ return 1;
+ }
/* Following flags need at least 2 groups */
if (sd->flags & (SD_LOAD_BALANCE |
@@ -5805,6 +5806,10 @@ static int sd_degenerate(struct sched_domain *sd)
SD_SHARE_PKG_RESOURCES |
SD_PREFER_SIBLING |
SD_SHARE_POWERDOMAIN);
+ if (parent->groups->sge) {
+ parent->flags &= ~SD_LOAD_BALANCE;
+ return 0;
+ }
if (nr_node_ids == 1)
pflags &= ~SD_SERIALIZE;
}
@@ -7098,8 +7103,6 @@ static int build_sched_domains(const struct cpumask *cpu_map,
*per_cpu_ptr(d.sd, i) = sd;
if (tl->flags & SDTL_OVERLAP || sched_feat(FORCE_SD_OVERLAP))
sd->flags |= SD_OVERLAP;
- if (cpumask_equal(cpu_map, sched_domain_span(sd)))
- break;
}
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fa393d9..c7d9bbf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7457,6 +7457,9 @@ static inline enum fbq_type fbq_classify_rq(struct rq *rq)
}
#endif /* CONFIG_NUMA_BALANCING */
+#define lb_sd_parent(sd) \
+ (sd->parent && sd->parent->groups != sd->parent->groups->next)
+
/**
* update_sd_lb_stats - Update sched_domain's statistics for load balancing.
* @env: The load balancing environment.
@@ -7530,7 +7533,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
- if (!env->sd->parent) {
+ if (!lb_sd_parent(env->sd)) {
/* update overload indicator if we are at root domain */
if (env->dst_rq->rd->overload != overload)
env->dst_rq->rd->overload = overload;
@@ -7989,7 +7992,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
int *continue_balancing)
{
int ld_moved, cur_ld_moved, active_balance = 0;
- struct sched_domain *sd_parent = sd->parent;
+ struct sched_domain *sd_parent = lb_sd_parent(sd) ? sd->parent : NULL;
struct sched_group *group;
struct rq *busiest;
unsigned long flags;
--
1.9.1
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