linux-kernel - Re: [RFC PATCH 02/10] sched: Task placement for heterogeneous systems based on task load-tracking

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Date:	Thu, 4 Oct 2012 12:24:35 +0530
From:	Amit Kucheria <amit.kucheria@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	morten.rasmussen@....com, paulmck@...ux.vnet.ibm.com,
	pjt@...gle.com, peterz@...radead.org, suresh.b.siddha@...el.com,
	linaro-sched-sig@...ts.linaro.org, linaro-dev@...ts.linaro.org,
	linux-kernel@...r.kernel.org,
	Robin Randhawa <robin.randhawa@....com>, Arvind.Chauhan@....com
Subject: Re: [RFC PATCH 02/10] sched: Task placement for heterogeneous systems
 based on task load-tracking

On Thu, Oct 4, 2012 at 11:32 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> Hi Morten,
>
> On 22 September 2012 00:02,  <morten.rasmussen@....com> wrote:
>> From: Morten Rasmussen <morten.rasmussen@....com>
>>
>> This patch introduces the basic SCHED_HMP infrastructure. Each class of
>> cpus is represented by a hmp_domain and tasks will only be moved between
>> these domains when their load profiles suggest it is beneficial.
>>
>> SCHED_HMP relies heavily on the task load-tracking introduced in Paul
>> Turners fair group scheduling patch set:
>>
>> <https://lkml.org/lkml/2012/8/23/267>
>>
>> SCHED_HMP requires that the platform implements arch_get_hmp_domains()
>> which should set up the platform specific list of hmp_domains. It is
>> also assumed that the platform disables SD_LOAD_BALANCE for the
>> appropriate sched_domains.
>
> An explanation of this requirement would be helpful here.
>
>> Tasks placement takes place every time a task is to be inserted into
>> a runqueue based on its load history. The task placement decision is
>> based on load thresholds.
>>
>> There are no restrictions on the number of hmp_domains, however,
>> multiple (>2) has not been tested and the up/down migration policy is
>> rather simple.
>>
>> Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
>> ---
>>  arch/arm/Kconfig      |   17 +++++
>>  include/linux/sched.h |    6 ++
>>  kernel/sched/fair.c   |  168 +++++++++++++++++++++++++++++++++++++++++++++++++
>>  kernel/sched/sched.h  |    6 ++
>>  4 files changed, 197 insertions(+)
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index f4a5d58..5b09684 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -1554,6 +1554,23 @@ config SCHED_SMT
>>           MultiThreading at a cost of slightly increased overhead in some
>>           places. If unsure say N here.
>>
>> +config DISABLE_CPU_SCHED_DOMAIN_BALANCE
>> +       bool "(EXPERIMENTAL) Disable CPU level scheduler load-balancing"
>> +       help
>> +         Disables scheduler load-balancing at CPU sched domain level.
>
> Shouldn't this depend on EXPERIMENTAL?

EXPERIMENTAL might be on its way out: https://lkml.org/lkml/2012/10/2/398
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