2 files changed, 33 insertions, 0 deletions

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 5dfdc9ea180b..46455961a88f 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -263,6 +263,26 @@ 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 4aa9f5bc6b2d..8068d97ce141 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 */
@@ -4085,6 +4094,10 @@ 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]);