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Subject: Re: [PATCH v4 2/4] sched/core: Propagate parent task's latency
 requirements to the child task
To:     Pavan Kondeti <pkondeti@codeaurora.org>
Cc:     linux-kernel@vger.kernel.org, peterz@infradead.org,
        mingo@redhat.com, vincent.guittot@linaro.org,
        dietmar.eggemann@arm.com, qais.yousef@arm.com,
        chris.hyser@oracle.com, patrick.bellasi@matbug.net,
        valentin.schneider@arm.com, David.Laight@ACULAB.COM,
        pjt@google.com, pavel@ucw.cz, tj@kernel.org,
        dhaval.giani@oracle.com, qperret@google.com,
        tim.c.chen@linux.intel.com
References: <20200224085918.16955-1-parth@linux.ibm.com>
 <20200224085918.16955-3-parth@linux.ibm.com>
 <20200225063226.GJ28029@codeaurora.org>
From:   Parth Shah <parth@linux.ibm.com>
Date:   Tue, 25 Feb 2020 13:46:19 +0530
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On 2/25/20 12:02 PM, Pavan Kondeti wrote:
> On Mon, Feb 24, 2020 at 02:29:16PM +0530, Parth Shah wrote:
>> Clone parent task's latency_nice attribute to the forked child task.
>>
>> Reset the latency_nice value to default value when the child task is
>> set to sched_reset_on_fork.
>>
>> Signed-off-by: Parth Shah <parth@linux.ibm.com>
>> Reviewed-by: Qais Yousef <qais.yousef@arm.com>
>> ---
>>  kernel/sched/core.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 377ec26e9159..65b6c00d6dac 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -2860,6 +2860,9 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
>>  	 */
>>  	p->prio = current->normal_prio;
>>  
>> +	/* Propagate the parent's latency requirements to the child as well */
>> +	p->latency_nice = current->latency_nice;
>> +
>>  	uclamp_fork(p);
>>  
>>  	/*
>> @@ -2876,6 +2879,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
>>  		p->prio = p->normal_prio = __normal_prio(p);
>>  		set_load_weight(p, false);
>>  
>> +		p->latency_nice = DEFAULT_LATENCY_NICE;
>>  		/*
>>  		 * We don't need the reset flag anymore after the fork. It has
>>  		 * fulfilled its duty:
>> -- 
>> 2.17.2
>>
> 
> LGTM.
> 
> latency_nice value initialization is missing for the init_task.

good catch. Will add that part too. Thanks for pointing out.

- Parth

> 
> Thanks,
> Pavan
>