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From: Parth Shah <parth@linux.ibm.com>
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
Subject: Re: [PATCH v4 3/4] sched: Allow sched_{get,set}attr to change latency_nice of the task
Date: Tue, 25 Feb 2020 20:33:53 +0530	[thread overview]
Message-ID: <f44fb56c-d9d9-a132-d953-bcbee8c03dda@linux.ibm.com> (raw)
In-Reply-To: <20200225065409.GK28029@codeaurora.org>



On 2/25/20 12:24 PM, Pavan Kondeti wrote:
> On Mon, Feb 24, 2020 at 02:29:17PM +0530, Parth Shah wrote:
> 
> [...]
> 
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 65b6c00d6dac..e1dc536d4ca3 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -4723,6 +4723,8 @@ static void __setscheduler_params(struct task_struct *p,
>>  	p->rt_priority = attr->sched_priority;
>>  	p->normal_prio = normal_prio(p);
>>  	set_load_weight(p, true);
>> +
>> +	p->latency_nice = attr->sched_latency_nice;
>>  }
> 
> We don't want this when SCHED_FLAG_LATENCY_NICE is not set in
> attr->flags.
> 
> The user may pass SCHED_FLAG_KEEP_PARAMS | SCHED_FLAG_LATENCY_NICE to
> change only latency nice value. So we have to update latency_nice
> outside __setscheduler_params(), I think.


AFAICT, passing SCHED_FLAG_KEEP_PARAMS with any other flag will prevent us
from changing the latency_nice value because of the below code flow:

__sched_setscheduler()
	__setscheduler()
		if (attr->sched_flags & SCHED_FLAG_KEEP_PARAMS) return;
		__setscheduler_params()

whereas, one thing we still can do is add if condition when setting the
value, i.e.,

@@ -4724,7 +4724,8 @@ static void __setscheduler_params(struct task_struct *p,
        p->normal_prio = normal_prio(p);
        set_load_weight(p, true);

-       p->latency_nice = attr->sched_latency_nice;
+       if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE)
+               p->latency_nice = attr->sched_latency_nice;
 }


> 
>>  
>>  /* Actually do priority change: must hold pi & rq lock. */
>> @@ -4880,6 +4882,13 @@ static int __sched_setscheduler(struct task_struct *p,
>>  			return retval;
>>  	}
>>  
>> +	if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE) {
>> +		if (attr->sched_latency_nice > MAX_LATENCY_NICE)
>> +			return -EINVAL;
>> +		if (attr->sched_latency_nice < MIN_LATENCY_NICE)
>> +			return -EINVAL;
>> +	}
>> +
>>  	if (pi)
>>  		cpuset_read_lock();
>>  
>> @@ -4914,6 +4923,9 @@ static int __sched_setscheduler(struct task_struct *p,
>>  			goto change;
>>  		if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
>>  			goto change;
>> +		if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE &&
>> +		    attr->sched_latency_nice != p->latency_nice)
>> +			goto change;
>>  
>>  		p->sched_reset_on_fork = reset_on_fork;
>>  		retval = 0;
>> @@ -5162,6 +5174,9 @@ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *a
>>  	    size < SCHED_ATTR_SIZE_VER1)
>>  		return -EINVAL;
>>  
>> +	if ((attr->sched_flags & SCHED_FLAG_LATENCY_NICE) &&
>> +	    size < SCHED_ATTR_SIZE_VER2)
>> +		return -EINVAL;
>>  	/*
>>  	 * XXX: Do we want to be lenient like existing syscalls; or do we want
>>  	 * to be strict and return an error on out-of-bounds values?
>> @@ -5391,6 +5406,8 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
>>  	else
>>  		kattr.sched_nice = task_nice(p);
>>  
>> +	kattr.sched_latency_nice = p->latency_nice;
>> +
> 
> Can you consider printing latency_nice value in proc_sched_show_task() in this
> patch/series?

Sure, I will add it.


Thanks,
Parth


  reply	other threads:[~2020-02-25 15:04 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-24  8:59 [PATCH v4 0/4] Introduce per-task latency_nice for scheduler hints Parth Shah
2020-02-24  8:59 ` [PATCH v4 1/4] sched: Introduce latency-nice as a per-task attribute Parth Shah
2020-02-24  8:59 ` [PATCH v4 2/4] sched/core: Propagate parent task's latency requirements to the child task Parth Shah
2020-02-25  6:32   ` Pavan Kondeti
2020-02-25  8:16     ` Parth Shah
2020-02-24  8:59 ` [PATCH v4 3/4] sched: Allow sched_{get,set}attr to change latency_nice of the task Parth Shah
2020-02-25  6:54   ` Pavan Kondeti
2020-02-25 15:03     ` Parth Shah [this message]
2020-02-26  3:44       ` Pavan Kondeti
2020-02-24  8:59 ` [PATCH v4 4/4] sched/core: Add permission checks for setting the latency_nice value Parth Shah
2020-02-24 13:29   ` Qais Yousef
2020-02-25  6:47     ` Parth Shah
2020-02-27 11:44       ` Qais Yousef
2020-02-27 14:46         ` chris hyser
2020-02-24 23:08   ` chris hyser

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