From: Arjan van de Ven <arjan@linux.intel.com>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: mingo@kernel.org, peterz@infradead.org,
vincent.guittot@linaro.org, preeti@linux.vnet.ibm.com,
alex.shi@intel.com, efault@gmx.de, pjt@google.com,
len.brown@intel.com, corbet@lwn.net, akpm@linux-foundation.org,
torvalds@linux-foundation.org, tglx@linutronix.de,
catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
linaro-kernel@lists.linaro.org
Subject: Re: [RFC][PATCH 1/9] sched: Introduce power scheduler
Date: Tue, 09 Jul 2013 19:10:15 -0700 [thread overview]
Message-ID: <51DCC287.40808@linux.intel.com> (raw)
In-Reply-To: <1373385338-12983-2-git-send-email-morten.rasmussen@arm.com>
On 7/9/2013 8:55 AM, Morten Rasmussen wrote:
> + mod_delayed_work_on(schedule_cpu(), system_wq, &dwork,
> + msecs_to_jiffies(INTERVAL));
so thinking about this more, this really really should not be a work queue.
a work queue will cause a large number of context switches for no reason
(on Intel and AMD you can switch P state from interrupt context, and I'm pretty sure
that holds for many ARM as well)
and in addition, it causes some really nasty cases, especially around real time tasks.
Your workqueue will schedule a kernel thread, which will run
BEHIND real time tasks, and such real time task will then never be able to start running at a higher performance.
(and with the delta between lowest and highest performance sometimes being 10x or more,
the real time task will be running SLOW... quite possible longer than several milliseconds)
and all for no good reason; a normal timer running in irq context would be much better for this kind of thing!
next prev parent reply other threads:[~2013-07-10 2:10 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-09 15:55 [RFC][PATCH 0/9] sched: Power scheduler design proposal Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 1/9] sched: Introduce power scheduler Morten Rasmussen
2013-07-09 16:48 ` Arjan van de Ven
2013-07-10 2:10 ` Arjan van de Ven [this message]
2013-07-10 11:11 ` Morten Rasmussen
2013-07-10 11:19 ` Vincent Guittot
2013-07-09 15:55 ` [RFC][PATCH 2/9] sched: Redirect update_cpu_power to sched/power.c Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 3/9] sched: Make select_idle_sibling() skip cpu with a cpu_power of 1 Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 4/9] sched: Make periodic load-balance disregard cpus " Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 5/9] sched: Make idle_balance() skip " Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 6/9] sched: power: add power_domain data structure Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 7/9] sched: power: Add power driver interface Morten Rasmussen
2013-07-09 15:55 ` [RFC][PATCH 8/9] sched: power: Add initial frequency scaling support to power scheduler Morten Rasmussen
2013-07-10 13:10 ` Arjan van de Ven
2013-07-12 12:51 ` Morten Rasmussen
2013-07-12 13:06 ` Catalin Marinas
2013-07-12 15:37 ` Arjan van de Ven
2013-07-09 15:55 ` [RFC][PATCH 9/9] sched: power: cpufreq: Initial schedpower cpufreq governor Morten Rasmussen
2013-07-09 16:58 ` [RFC][PATCH 0/9] sched: Power scheduler design proposal Arjan van de Ven
2013-07-10 11:16 ` Morten Rasmussen
2013-07-10 13:05 ` Arjan van de Ven
2013-07-12 12:46 ` Morten Rasmussen
2013-07-12 15:35 ` Arjan van de Ven
2013-07-12 13:00 ` Catalin Marinas
2013-07-12 15:44 ` Arjan van de Ven
2013-07-11 11:34 ` Preeti U Murthy
2013-07-12 13:48 ` Morten Rasmussen
2013-07-15 3:43 ` Preeti U Murthy
2013-07-15 9:55 ` Catalin Marinas
2013-07-15 15:24 ` Arjan van de Ven
2013-07-12 13:31 ` Catalin Marinas
2013-07-13 6:49 ` Peter Zijlstra
2013-07-13 10:23 ` Catalin Marinas
2013-07-15 7:53 ` Vincent Guittot
2013-07-15 20:39 ` Peter Zijlstra
2013-07-16 12:42 ` Catalin Marinas
2013-07-16 15:23 ` Arjan van de Ven
2013-07-17 14:14 ` Catalin Marinas
2013-07-24 13:50 ` Morten Rasmussen
2013-07-24 15:16 ` Arjan van de Ven
2013-07-24 16:46 ` Morten Rasmussen
2013-07-24 16:48 ` Arjan van de Ven
2013-07-25 8:00 ` Morten Rasmussen
2013-07-13 14:40 ` Arjan van de Ven
2013-07-15 19:59 ` Peter Zijlstra
2013-07-15 20:37 ` Arjan van de Ven
2013-07-15 21:03 ` Peter Zijlstra
2013-07-15 22:46 ` Arjan van de Ven
2013-07-16 20:45 ` David Lang
2013-07-15 20:41 ` Arjan van de Ven
2013-07-15 21:06 ` Peter Zijlstra
2013-07-15 21:12 ` Peter Zijlstra
2013-07-15 22:52 ` Arjan van de Ven
2013-07-16 17:38 ` Peter Zijlstra
2013-07-16 18:44 ` Arjan van de Ven
2013-07-16 19:21 ` Peter Zijlstra
2013-07-16 19:57 ` Arjan van de Ven
2013-07-16 20:17 ` Peter Zijlstra
2013-07-16 20:21 ` Arjan van de Ven
2013-07-16 20:32 ` Arjan van de Ven
2013-07-15 22:46 ` Arjan van de Ven
2013-07-13 16:14 ` Arjan van de Ven
2013-07-15 2:05 ` Alex Shi
2013-07-24 13:16 ` Morten Rasmussen
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