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authorLinus Torvalds <torvalds@linux-foundation.org>2013-07-02 19:53:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-02 19:53:30 -0700
commitf317ff9eed763e99bd226a447f93d42509434f43 (patch)
treed77edfcdb1e7c32c30327f50dce04bcff8ec1531 /kernel
parent13cc56013842a847a0f6ff805d9ed9181e753ef8 (diff)
parenta85f1a41f020bc2c97611060bcfae6f48a1db28d (diff)
Merge branch 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue changes from Tejun Heo: "Surprisingly, Lai and I didn't break too many things implementing custom pools and stuff last time around and there aren't any follow-up changes necessary at this point. The only change in this pull request is Viresh's patches to make some per-cpu workqueues to behave as unbound workqueues dependent on a boot param whose default can be configured via a config option. This leads to higher processing overhead / lower bandwidth as more work items are bounced across CPUs; however, it can lead to noticeable powersave in certain configurations - ~10% w/ idlish constant workload on a big.LITTLE configuration according to Viresh. This is because per-cpu workqueues interfere with how the scheduler perceives whether or not each CPU is idle by forcing pinned tasks on them, which makes the scheduler's power-aware scheduling decisions less effective. Its effectiveness is likely less pronounced on homogenous configurations and this type of optimization can probably be made automatic; however, the changes are pretty minimal and the affected workqueues are clearly marked, so it's an easy gain for some configurations for the time being with pretty unintrusive changes." * 'for-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: fbcon: queue work on power efficient wq block: queue work on power efficient wq PHYLIB: queue work on system_power_efficient_wq workqueue: Add system wide power_efficient workqueues workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqueues
Diffstat (limited to 'kernel')
-rw-r--r--kernel/power/Kconfig20
-rw-r--r--kernel/workqueue.c26
2 files changed, 45 insertions, 1 deletions
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 9c39de095ba9..d444c4e834f4 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -262,6 +262,26 @@ config PM_GENERIC_DOMAINS
bool
depends on PM
+config WQ_POWER_EFFICIENT_DEFAULT
+ bool "Enable workqueue power-efficient mode by default"
+ depends on PM
+ default n
+ help
+ Per-cpu workqueues are generally preferred because they show
+ better performance thanks to cache locality; unfortunately,
+ per-cpu workqueues tend to be more power hungry than unbound
+ workqueues.
+
+ Enabling workqueue.power_efficient kernel parameter makes the
+ per-cpu workqueues which were observed to contribute
+ significantly to power consumption unbound, leading to measurably
+ lower power usage at the cost of small performance overhead.
+
+ This config option determines whether workqueue.power_efficient
+ is enabled by default.
+
+ If in doubt, say N.
+
config PM_GENERIC_DOMAINS_SLEEP
def_bool y
depends on PM_SLEEP && PM_GENERIC_DOMAINS
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ee8e29a2320c..f02c4a4a0c3c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -272,6 +272,15 @@ static cpumask_var_t *wq_numa_possible_cpumask;
static bool wq_disable_numa;
module_param_named(disable_numa, wq_disable_numa, bool, 0444);
+/* see the comment above the definition of WQ_POWER_EFFICIENT */
+#ifdef CONFIG_WQ_POWER_EFFICIENT_DEFAULT
+static bool wq_power_efficient = true;
+#else
+static bool wq_power_efficient;
+#endif
+
+module_param_named(power_efficient, wq_power_efficient, bool, 0444);
+
static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
@@ -305,6 +314,10 @@ struct workqueue_struct *system_unbound_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_unbound_wq);
struct workqueue_struct *system_freezable_wq __read_mostly;
EXPORT_SYMBOL_GPL(system_freezable_wq);
+struct workqueue_struct *system_power_efficient_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_power_efficient_wq);
+struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
+EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
static int worker_thread(void *__worker);
static void copy_workqueue_attrs(struct workqueue_attrs *to,
@@ -4086,6 +4099,10 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
struct workqueue_struct *wq;
struct pool_workqueue *pwq;
+ /* see the comment above the definition of WQ_POWER_EFFICIENT */
+ if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
+ flags |= WQ_UNBOUND;
+
/* allocate wq and format name */
if (flags & WQ_UNBOUND)
tbl_size = wq_numa_tbl_len * sizeof(wq->numa_pwq_tbl[0]);
@@ -4985,8 +5002,15 @@ static int __init init_workqueues(void)
WQ_UNBOUND_MAX_ACTIVE);
system_freezable_wq = alloc_workqueue("events_freezable",
WQ_FREEZABLE, 0);
+ system_power_efficient_wq = alloc_workqueue("events_power_efficient",
+ WQ_POWER_EFFICIENT, 0);
+ system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
+ WQ_FREEZABLE | WQ_POWER_EFFICIENT,
+ 0);
BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
- !system_unbound_wq || !system_freezable_wq);
+ !system_unbound_wq || !system_freezable_wq ||
+ !system_power_efficient_wq ||
+ !system_freezable_power_efficient_wq);
return 0;
}
early_initcall(init_workqueues);