[v2,3/4] sched/deadline: add the "set_flag" argument to cpudl_find()

Message ID 1416411982-1204-3-git-send-email-pang.xunlei@linaro.org
State New
Headers show

Commit Message

pang.xunlei Nov. 19, 2014, 3:46 p.m.
The call site of cpudl_find() in check_preempt_equal_dl() doesn't
use later_mask, so add this extra argument to distinquish the case.

Signed-off-by: pang.xunlei <pang.xunlei@linaro.org>
---
 kernel/sched/cpudeadline.c |    6 ++++--
 kernel/sched/cpudeadline.h |    2 +-
 kernel/sched/deadline.c    |    6 +++---
 3 files changed, 8 insertions(+), 6 deletions(-)

Comments

Steven Rostedt Nov. 19, 2014, 4:24 p.m. | #1
On Wed, 19 Nov 2014 23:46:21 +0800
"pang.xunlei" <pang.xunlei@linaro.org> wrote:

> The call site of cpudl_find() in check_preempt_equal_dl() doesn't
> use later_mask, so add this extra argument to distinquish the case.
> 
> Signed-off-by: pang.xunlei <pang.xunlei@linaro.org>
> ---
>  kernel/sched/cpudeadline.c |    6 ++++--
>  kernel/sched/cpudeadline.h |    2 +-
>  kernel/sched/deadline.c    |    6 +++---
>  3 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index c01b3aa..3047846 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -98,11 +98,12 @@ static inline int cpudl_maximum(struct cpudl *cp)
>   * @cp: the cpudl max-heap context
>   * @p: the task
>   * @later_mask: a mask to fill in with the selected CPUs (not NULL)
> + * @set_flag: indicate if later_mask should be set
>   *
>   * Returns: int - best CPU (heap maximum if suitable)
>   */
>  int cpudl_find(struct cpudl *cp, struct task_struct *p,
> -	       struct cpumask *later_mask)
> +	       struct cpumask *later_mask, int set_flag)

set_flag should be a bool type.

>  {
>  	int best_cpu = -1;
>  	const struct sched_dl_entity *dl_se = &p->dl;
> @@ -114,7 +115,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>  	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
>  			dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
>  		best_cpu = cpudl_maximum(cp);
> -		cpumask_set_cpu(best_cpu, later_mask);
> +		if (set_flag)
> +			cpumask_set_cpu(best_cpu, later_mask);

I'm not sure this is worth it. cpumask_set_cpu() is rather efficient.

>  	}
>  
>  out:

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pang.xunlei Nov. 20, 2014, 2:58 p.m. | #2
On 20 November 2014 00:24, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Wed, 19 Nov 2014 23:46:21 +0800
> "pang.xunlei" <pang.xunlei@linaro.org> wrote:
>
>> The call site of cpudl_find() in check_preempt_equal_dl() doesn't
>> use later_mask, so add this extra argument to distinquish the case.
>>
>> Signed-off-by: pang.xunlei <pang.xunlei@linaro.org>
>> ---
>>  kernel/sched/cpudeadline.c |    6 ++++--
>>  kernel/sched/cpudeadline.h |    2 +-
>>  kernel/sched/deadline.c    |    6 +++---
>>  3 files changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>> index c01b3aa..3047846 100644
>> --- a/kernel/sched/cpudeadline.c
>> +++ b/kernel/sched/cpudeadline.c
>> @@ -98,11 +98,12 @@ static inline int cpudl_maximum(struct cpudl *cp)
>>   * @cp: the cpudl max-heap context
>>   * @p: the task
>>   * @later_mask: a mask to fill in with the selected CPUs (not NULL)
>> + * @set_flag: indicate if later_mask should be set
>>   *
>>   * Returns: int - best CPU (heap maximum if suitable)
>>   */
>>  int cpudl_find(struct cpudl *cp, struct task_struct *p,
>> -            struct cpumask *later_mask)
>> +            struct cpumask *later_mask, int set_flag)
>
> set_flag should be a bool type.
>
>>  {
>>       int best_cpu = -1;
>>       const struct sched_dl_entity *dl_se = &p->dl;
>> @@ -114,7 +115,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>>       } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
>>                       dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
>>               best_cpu = cpudl_maximum(cp);
>> -             cpumask_set_cpu(best_cpu, later_mask);
>> +             if (set_flag)
>> +                     cpumask_set_cpu(best_cpu, later_mask);
>
> I'm not sure this is worth it. cpumask_set_cpu() is rather efficient.
HI Steve,

Thanks for your commenting, I've rethinked this a bit.
We can do a little trick with its return value, then could avoid this
extra cpumask_set_cpu() without this extra set_flag:
1) define macros for the return values of cpudl_find(), like:
#define    CPUDL_FIND_NONE          -2  /* no available cpus */
#define    CPUDL_FIND_CPUMASK   -1  /* available cpus in later_mask */

then, with the return value >=0, means it returns the only one available cpu.

2) In the leg of "if", it can just return CPUDL_FIND_CPUMASK, as we
want to select the best_cpu in find_later_rq().
In the leg of "else if", just returns cpudl_maximum(cp), apparently
there is no need to set the later_mask, since we will definitely
select this cpu as the best_cpu in find_later_rq() .

int cpudl_find(struct cpudl *cp, struct task_struct *p,
           struct cpumask *later_mask)
{
    const struct sched_dl_entity *dl_se = &p->dl;

    cpumask_and(later_mask, &p->cpus_allowed, &p->cpus_allowed);
    if (cpumask_and(later_mask, later_mask, cp->free_cpus)) {
        return CPUDL_FIND_CPUMASK;
    } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
                dl_time_before(dl_se->deadline, cp->elements[0].dl))
        int cpu;

        cpu = cpudl_maximum(cp);
        WARN_ON(!cpu_present(cpu));
        return cpu;
    }

out:

    return CPUDL_FIND_NONE;
}

Thus, in find_later_rq() we can change the call site code like:
    best_cpu = cpudl_find(&task_rq(task)->rd->cpudl, task,
                           later_mask);
    if (best_cpu == CPUDL_FIND_NONE)
        return -1;
    if (best_cpu != CPUDL_FIND_CPUMASK)
        return best_cpu;

    /* adjust the following code as that in RT find_lowest_rq(), omit here... */

What's your view about this?

Thanks,
Xunlei
>
>>       }
>>
>>  out:
>
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pang.xunlei Nov. 20, 2014, 3:06 p.m. | #3
On 20 November 2014 22:58, pang.xunlei <pang.xunlei@linaro.org> wrote:
> On 20 November 2014 00:24, Steven Rostedt <rostedt@goodmis.org> wrote:
>> On Wed, 19 Nov 2014 23:46:21 +0800
>> "pang.xunlei" <pang.xunlei@linaro.org> wrote:
>>
>>> The call site of cpudl_find() in check_preempt_equal_dl() doesn't
>>> use later_mask, so add this extra argument to distinquish the case.
>>>
>>> Signed-off-by: pang.xunlei <pang.xunlei@linaro.org>
>>> ---
>>>  kernel/sched/cpudeadline.c |    6 ++++--
>>>  kernel/sched/cpudeadline.h |    2 +-
>>>  kernel/sched/deadline.c    |    6 +++---
>>>  3 files changed, 8 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>>> index c01b3aa..3047846 100644
>>> --- a/kernel/sched/cpudeadline.c
>>> +++ b/kernel/sched/cpudeadline.c
>>> @@ -98,11 +98,12 @@ static inline int cpudl_maximum(struct cpudl *cp)
>>>   * @cp: the cpudl max-heap context
>>>   * @p: the task
>>>   * @later_mask: a mask to fill in with the selected CPUs (not NULL)
>>> + * @set_flag: indicate if later_mask should be set
>>>   *
>>>   * Returns: int - best CPU (heap maximum if suitable)
>>>   */
>>>  int cpudl_find(struct cpudl *cp, struct task_struct *p,
>>> -            struct cpumask *later_mask)
>>> +            struct cpumask *later_mask, int set_flag)
>>
>> set_flag should be a bool type.
>>
>>>  {
>>>       int best_cpu = -1;
>>>       const struct sched_dl_entity *dl_se = &p->dl;
>>> @@ -114,7 +115,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>>>       } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
>>>                       dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
>>>               best_cpu = cpudl_maximum(cp);
>>> -             cpumask_set_cpu(best_cpu, later_mask);
>>> +             if (set_flag)
>>> +                     cpumask_set_cpu(best_cpu, later_mask);
>>
>> I'm not sure this is worth it. cpumask_set_cpu() is rather efficient.
> HI Steve,
>
> Thanks for your commenting, I've rethinked this a bit.
> We can do a little trick with its return value, then could avoid this
> extra cpumask_set_cpu() without this extra set_flag:
> 1) define macros for the return values of cpudl_find(), like:
> #define    CPUDL_FIND_NONE          -2  /* no available cpus */
> #define    CPUDL_FIND_CPUMASK   -1  /* available cpus in later_mask */
>
> then, with the return value >=0, means it returns the only one available cpu.
>
> 2) In the leg of "if", it can just return CPUDL_FIND_CPUMASK, as we
> want to select the best_cpu in find_later_rq().
> In the leg of "else if", just returns cpudl_maximum(cp), apparently
> there is no need to set the later_mask, since we will definitely
> select this cpu as the best_cpu in find_later_rq() .
>
> int cpudl_find(struct cpudl *cp, struct task_struct *p,
>            struct cpumask *later_mask)
> {
>     const struct sched_dl_entity *dl_se = &p->dl;
>
>     cpumask_and(later_mask, &p->cpus_allowed, &p->cpus_allowed);
Apologies for this typo, it should be:
cpumask_and(later_mask, cpu_active_mask, &p->cpus_allowed);

>     if (cpumask_and(later_mask, later_mask, cp->free_cpus)) {
>         return CPUDL_FIND_CPUMASK;
>     } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
>                 dl_time_before(dl_se->deadline, cp->elements[0].dl))
>         int cpu;
>
>         cpu = cpudl_maximum(cp);
>         WARN_ON(!cpu_present(cpu));
>         return cpu;
>     }
>
> out:
also delete this lable.
>
>     return CPUDL_FIND_NONE;
> }
>
> Thus, in find_later_rq() we can change the call site code like:
>     best_cpu = cpudl_find(&task_rq(task)->rd->cpudl, task,
>                            later_mask);
>     if (best_cpu == CPUDL_FIND_NONE)
>         return -1;
>     if (best_cpu != CPUDL_FIND_CPUMASK)
>         return best_cpu;
>
>     /* adjust the following code as that in RT find_lowest_rq(), omit here... */
>
> What's your view about this?
>
> Thanks,
> Xunlei
>>
>>>       }
>>>
>>>  out:
>>
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Patch

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index c01b3aa..3047846 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -98,11 +98,12 @@  static inline int cpudl_maximum(struct cpudl *cp)
  * @cp: the cpudl max-heap context
  * @p: the task
  * @later_mask: a mask to fill in with the selected CPUs (not NULL)
+ * @set_flag: indicate if later_mask should be set
  *
  * Returns: int - best CPU (heap maximum if suitable)
  */
 int cpudl_find(struct cpudl *cp, struct task_struct *p,
-	       struct cpumask *later_mask)
+	       struct cpumask *later_mask, int set_flag)
 {
 	int best_cpu = -1;
 	const struct sched_dl_entity *dl_se = &p->dl;
@@ -114,7 +115,8 @@  int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
 			dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
 		best_cpu = cpudl_maximum(cp);
-		cpumask_set_cpu(best_cpu, later_mask);
+		if (set_flag)
+			cpumask_set_cpu(best_cpu, later_mask);
 	}
 
 out:
diff --git a/kernel/sched/cpudeadline.h b/kernel/sched/cpudeadline.h
index 4a10a65..a3a85e8 100644
--- a/kernel/sched/cpudeadline.h
+++ b/kernel/sched/cpudeadline.h
@@ -22,7 +22,7 @@  struct cpudl {
 #ifdef CONFIG_SMP
 int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	       struct cpumask *later_mask);
-void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid);
+void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid, int set_flag);
 int cpudl_init(struct cpudl *cp);
 void cpudl_set_freecpu(struct cpudl *cp, int cpu);
 void cpudl_cleanup(struct cpudl *cp);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 3ecf838..e8208d0 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -976,7 +976,7 @@  static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * let's hope p can move out.
 	 */
 	if (rq->curr->nr_cpus_allowed == 1 ||
-	    cpudl_find(&rq->rd->cpudl, rq->curr, later_mask) == -1)
+	    cpudl_find(&rq->rd->cpudl, rq->curr, later_mask, 0) == -1)
 		return;
 
 	/*
@@ -984,7 +984,7 @@  static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * see if it is pushed or pulled somewhere else.
 	 */
 	if (p->nr_cpus_allowed != 1 &&
-	    cpudl_find(&rq->rd->cpudl, p, later_mask) != -1)
+	    cpudl_find(&rq->rd->cpudl, p, later_mask, 0) != -1)
 		return;
 
 	resched_curr(rq);
@@ -1190,7 +1190,7 @@  static int find_later_rq(struct task_struct *task)
 	 * first, then we can look for a suitable cpu.
 	 */
 	best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
-			task, later_mask);
+			task, later_mask, 1);
 	if (best_cpu == -1)
 		return -1;