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Message-ID: <CAP245DW3RwTZBXX-gcYKGDcRqrO8E86a9Y1jWNCL2kOO4+UJmA@mail.gmail.com>
Date: Thu, 25 Apr 2013 16:43:52 +0530
From: Amit Kucheria <amit.kucheria@...aro.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: Tejun Heo <tj@...nel.org>, davem@...emloft.net,
linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
Robin Randhawa <robin.randhawa@....com>,
Charles Garcia-Tobin <charles.garcia-tobin@....com>,
Steve Bannister <Steve.Bannister@....com>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Arvind Chauhan <arvind.chauhan@....com>,
Patch Tracking <patches@...aro.org>, airlied@...hat.com,
mingo@...hat.com, Jens Axboe <axboe@...nel.dk>,
Liviu Dudau <Liviu.Dudau@....com>,
Lists linaro-kernel <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH V5 1/5] workqueues: Introduce new flag WQ_POWER_EFFICIENT
for power oriented workqueues
On Thu, Apr 25, 2013 at 9:13 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 25 April 2013 09:00, Amit Kucheria <amit.kucheria@...aro.org> wrote:
>> Yes. That was my intention - preventing a prompt on existing defconfigs and
>> there by maintaining current behavior.
>
> Hmm... Following is the version after fixing all problems you reported.
> @Tejun: I have attached it too as gmail's copy-paste may break it. Please
> consider applying this series if it looks fine to you.
>
>
> ---------------x----------------x---------------------
>
> From: Viresh Kumar <viresh.kumar@...aro.org>
> Date: Mon, 8 Apr 2013 16:45:40 +0530
> Subject: [PATCH V5 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 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 <viresh.kumar@...aro.org>
For the series, you can add my:
Reviewed-by: Amit Kucheria <amit.kucheria@...aro.org>
> ---
> Documentation/kernel-parameters.txt | 17 +++++++++++++++++
> include/linux/workqueue.h | 3 +++
> kernel/power/Kconfig | 19 +++++++++++++++++++
> kernel/workqueue.c | 11 +++++++++++
> 4 files changed, 50 insertions(+)
>
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index c4fa000..22edc83 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3312,6 +3312,23 @@ 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 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..018f039 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -263,6 +263,25 @@ 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 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 4aa9f5b..a327027 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]);
--
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