From 8b051a73ec68235589571a710130ddf4347527fc Mon Sep 17 00:00:00 2001 Message-Id: <8b051a73ec68235589571a710130ddf4347527fc.1368433695.git.viresh.kumar@linaro.org> From: Viresh Kumar Date: Mon, 8 Apr 2013 16:45:40 +0530 Subject: [PATCH V5 resent 1/5] workqueues: Introduce new flag WQ_POWER_EFFICIENT for power oriented workqueues Workqueues can be performance or power-oriented. Currently, most workqueues are bound to the CPU they were created on. This gives good performance (due to cache effects) at the cost of potentially waking up otherwise idle cores (Idle from scheduler's perspective. Which may or may not be physically idle) just to process some work. To save power, we can allow the work to be rescheduled on a core that is already awake. Workqueues created with the WQ_UNBOUND flag will allow some power savings. However, we don't change the default behaviour of the system. To enable power-saving behaviour, a new config option CONFIG_WQ_POWER_EFFICIENT needs to be turned on. This option can also be overridden by the workqueue.power_efficient boot parameter. Signed-off-by: Viresh Kumar Reviewed-by: Amit Kucheria --- Documentation/kernel-parameters.txt | 18 ++++++++++++++++++ include/linux/workqueue.h | 3 +++ kernel/power/Kconfig | 21 +++++++++++++++++++++ kernel/workqueue.c | 11 +++++++++++ 4 files changed, 53 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index c3bfacb..9a991b6 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3320,6 +3320,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted. that this also can be controlled per-workqueue for workqueues visible under /sys/bus/workqueue/. + workqueue.power_efficient + Workqueues can be performance or power-oriented. + Currently, most workqueues are bound to the CPU they + were created on. This gives good performance (due to + cache effects) at the cost of potentially waking up + otherwise idle cores (Idle from scheduler's perspective. + Which may or may not be physically idle) just to process + some work. To save power, we can allow the work to be + rescheduled on a core that is already awake. + + Workqueues created with the WQ_UNBOUND flag will allow + some power savings. However, we don't change the + default behaviour of the system. To enable power-saving + behaviour, a new config option CONFIG_WQ_POWER_EFFICIENT + needs to be turned on. This option can also be + overridden by the workqueue.power_efficient boot + parameter. + x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of default x2apic cluster mode on platforms supporting x2apic. diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 623488f..83fa570 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -302,6 +302,9 @@ enum { WQ_HIGHPRI = 1 << 4, /* high priority */ WQ_CPU_INTENSIVE = 1 << 5, /* cpu instensive workqueue */ WQ_SYSFS = 1 << 6, /* visible in sysfs, see wq_sysfs_register() */ + WQ_POWER_EFFICIENT = 1 << 7, /* WQ_UNBOUND, for power + * saving, if wq_power_efficient is + * enabled. Unused otherwise. */ __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */ __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */ diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index 5dfdc9e..e8c2b77 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -263,6 +263,27 @@ config PM_GENERIC_DOMAINS bool depends on PM +config WQ_POWER_EFFICIENT + bool "Workqueue allocated as UNBOUND (by default) for power efficiency" + depends on PM + default n + help + Workqueues can be performance or power-oriented. Currently, most + workqueues are bound to the CPU they were created on. This gives good + performance (due to cache effects) at the cost of potentially waking + up otherwise idle cores (Idle from scheduler's perspective. Which may + or may not be physically idle) just to process some work. To save + power, we can allow the work to be rescheduled on a core that is + already awake. + + Workqueues created with the WQ_UNBOUND flag will allow some power + savings. However, we don't change the default behaviour of the + system. To enable power-saving behaviour, a new config option + CONFIG_WQ_POWER_EFFICIENT needs to be turned on. This option can also + be overridden by the workqueue.power_efficient boot parameter. + + 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 1ae6028..9d8753e 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -272,6 +272,14 @@ static cpumask_var_t *wq_numa_possible_cpumask; static bool wq_disable_numa; module_param_named(disable_numa, wq_disable_numa, bool, 0444); +#ifdef CONFIG_WQ_POWER_EFFICIENT +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 +4093,9 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, struct workqueue_struct *wq; struct pool_workqueue *pwq; + 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]); -- 1.7.12.rc2.18.g61b472e