linux-kernel - Re: [RFC 1/3] Introduce latency-tolerance as an per-task attribute

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Date:   Tue, 3 Dec 2019 21:17:11 +0530
From:   Parth Shah <parth@...ux.ibm.com>
To:     Qais Yousef <qais.yousef@....com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...hat.com, vincent.guittot@...aro.org,
        patrick.bellasi@...bug.net, valentin.schneider@....com,
        pavel@....cz, dhaval.giani@...cle.com, qperret@...rret.net,
        David.Laight@...LAB.COM, morten.rasmussen@....com, pjt@...gle.com,
        tj@...nel.org, dietmar.eggemann@....com, viresh.kumar@...aro.org,
        rafael.j.wysocki@...el.com, daniel.lezcano@...aro.org
Subject: Re: [RFC 1/3] Introduce latency-tolerance as an per-task attribute



On 12/3/19 2:06 PM, Qais Yousef wrote:
> On 11/25/19 15:16, Parth Shah wrote:
>> Latency-tolerance indicates the latency requirements of a task with respect
>> to the other tasks in the system. The value of the attribute can be within
>> the range of [-20, 19] both inclusive to be in-line with the values just
>> like task nice values.
>>
>> latency_tolerance = -20 indicates the task to have the least latency as
>> compared to the tasks having latency_tolerance = +19.
>>
>> The latency_tolerance may affect only the CFS SCHED_CLASS by getting
>> latency requirements from the userspace.
>>
>> Signed-off-by: Parth Shah <parth@...ux.ibm.com>
>> ---
>>  include/linux/sched.h                   |  3 +++
>>  include/linux/sched/latency_tolerance.h | 13 +++++++++++++
>>  2 files changed, 16 insertions(+)
>>  create mode 100644 include/linux/sched/latency_tolerance.h
>>
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 2c2e56bd8913..bcc1c1d0856d 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -25,6 +25,7 @@
>>  #include <linux/resource.h>
>>  #include <linux/latencytop.h>
>>  #include <linux/sched/prio.h>
>> +#include <linux/sched/latency_tolerance.h>
>>  #include <linux/sched/types.h>
>>  #include <linux/signal_types.h>
>>  #include <linux/mm_types_task.h>
>> @@ -666,6 +667,8 @@ struct task_struct {
>>  #endif
>>  	int				on_rq;
>>  
>> +	int				latency_tolerance;
>> +
>>  	int				prio;
>>  	int				static_prio;
>>  	int				normal_prio;
>> diff --git a/include/linux/sched/latency_tolerance.h b/include/linux/sched/latency_tolerance.h
>> new file mode 100644
>> index 000000000000..7a00abe05bc4
>> --- /dev/null
>> +++ b/include/linux/sched/latency_tolerance.h
>> @@ -0,0 +1,13 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef _LINUX_SCHED_LATENCY_TOLERANCE_H
>> +#define _LINUX_SCHED_LATENCY_TOLERANCE_H
> 
> nit: Add some description here explaining what latency tolerance is please. You
> copy paste some text from your cover letter :)

Sure. Will add some text here.

> 
> --
> Qais Youesf
> 
>> +
>> +#define MAX_LATENCY_TOLERANCE	19
>> +#define MIN_LATENCY_TOLERANCE	-20
>> +
>> +#define LATENCY_TOLERANCE_WIDTH	\
>> +	(MAX_LATENCY_TOLERANCE - MIN_LATENCY_TOLERANCE + 1)
>> +
>> +#define DEFAULT_LATENCY_TOLERANCE	0
>> +
>> +#endif /* _LINUX_SCHED_LATENCY_TOLERANCE_H */
>> -- 
>> 2.17.2
>>