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Date: Tue, 4 Jun 2024 14:53:08 +0100
From: Metin Kaya <metin.kaya@....com>
To: Qais Yousef <qyousef@...alina.io>, John Stultz <jstultz@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Connor O'Brien <connoro@...gle.com>,
Joel Fernandes <joelaf@...gle.com>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Valentin Schneider <vschneid@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
Zimuzo Ezeozue <zezeozue@...gle.com>, Youssef Esmat
<youssefesmat@...gle.com>, Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
Boqun Feng <boqun.feng@...il.com>, "Paul E. McKenney" <paulmck@...nel.org>,
Xuewen Yan <xuewen.yan94@...il.com>, K Prateek Nayak
<kprateek.nayak@....com>, Thomas Gleixner <tglx@...utronix.de>,
kernel-team@...roid.com
Subject: Re: [PATCH v10 5/7] sched: Consolidate pick_*_task to
task_is_pushable helper
On 04/06/2024 2:18 pm, Qais Yousef wrote:
> On 05/06/24 21:54, John Stultz wrote:
>> From: Connor O'Brien <connoro@...gle.com>
>>
>> This patch consolidates rt and deadline pick_*_task functions to
>> a task_is_pushable() helper
>>
>> This patch was broken out from a larger chain migration
>> patch originally by Connor O'Brien.
>>
>> Cc: Joel Fernandes <joelaf@...gle.com>
>> Cc: Qais Yousef <qyousef@...alina.io>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Juri Lelli <juri.lelli@...hat.com>
>> Cc: Vincent Guittot <vincent.guittot@...aro.org>
>> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
>> Cc: Valentin Schneider <vschneid@...hat.com>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Cc: Ben Segall <bsegall@...gle.com>
>> Cc: Zimuzo Ezeozue <zezeozue@...gle.com>
>> Cc: Youssef Esmat <youssefesmat@...gle.com>
>> Cc: Mel Gorman <mgorman@...e.de>
>> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Waiman Long <longman@...hat.com>
>> Cc: Boqun Feng <boqun.feng@...il.com>
>> Cc: "Paul E. McKenney" <paulmck@...nel.org>
>> Cc: Metin Kaya <Metin.Kaya@....com>
>> Cc: Xuewen Yan <xuewen.yan94@...il.com>
>> Cc: K Prateek Nayak <kprateek.nayak@....com>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: kernel-team@...roid.com
>> Tested-by: K Prateek Nayak <kprateek.nayak@....com>
>> Tested-by: Metin Kaya <metin.kaya@....com>
>> Reviewed-by: Metin Kaya <metin.kaya@....com>
>> Reviewed-by: Valentin Schneider <vschneid@...hat.com>
>> Signed-off-by: Connor O'Brien <connoro@...gle.com>
>> [jstultz: split out from larger chain migration patch,
>> renamed helper function]
>> Signed-off-by: John Stultz <jstultz@...gle.com>
>> ---
>> v7:
>> * Split from chain migration patch
>> * Renamed function
>> ---
>> kernel/sched/deadline.c | 10 +---------
>> kernel/sched/rt.c | 11 +----------
>> kernel/sched/sched.h | 10 ++++++++++
>> 3 files changed, 12 insertions(+), 19 deletions(-)
>>
>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>> index eaedc69c5e30..ae583a427539 100644
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -2179,14 +2179,6 @@ static void task_fork_dl(struct task_struct *p)
>> /* Only try algorithms three times */
>> #define DL_MAX_TRIES 3
>>
>> -static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
>> -{
>> - if (!task_on_cpu(rq, p) &&
>> - cpumask_test_cpu(cpu, &p->cpus_mask))
>> - return 1;
>> - return 0;
>> -}
>> -
>> /*
>> * Return the earliest pushable rq's task, which is suitable to be executed
>> * on the CPU, NULL otherwise:
>> @@ -2205,7 +2197,7 @@ static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu
>> if (next_node) {
>> p = __node_2_pdl(next_node);
>>
>> - if (pick_dl_task(rq, p, cpu))
>> + if (task_is_pushable(rq, p, cpu) == 1)
>
> Any reason we're checking specifically for == 1? Could the function later
> return something other than 0 or 1?
I hear you, but just letting you know that `task_is_pushable()` will
return different non-zero results per upcoming patches in the queue. The
commit "sched: Fix rt/dl load balancing via chain level balance" will
make the function look like below (excerpt from `kernel/sched/core.c`):
/*
* Returns:
* 1 if chain is pushable and affinity does not prevent pushing to cpu
* 0 if chain is unpushable
* -1 if chain is pushable but affinity blocks running on cpu.
*/
int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu)
>
> It's explaining if 1 could end up meaning something else in the commit message
> and in function docs. Otherwise let's make it a bool and not do explicit check
> for return value.
>
> With this
>
> Reviewed-by: Qais Yousef <qyousef@...alina.io>
>
>> return p;
>>
>> next_node = rb_next(next_node);
>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>> index 975cb49a64dc..8b6fb77e095b 100644
>> --- a/kernel/sched/rt.c
>> +++ b/kernel/sched/rt.c
>> @@ -1791,15 +1791,6 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
>> /* Only try algorithms three times */
>> #define RT_MAX_TRIES 3
>>
>> -static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
>> -{
>> - if (!task_on_cpu(rq, p) &&
>> - cpumask_test_cpu(cpu, &p->cpus_mask))
>> - return 1;
>> -
>> - return 0;
>> -}
>> -
>> /*
>> * Return the highest pushable rq's task, which is suitable to be executed
>> * on the CPU, NULL otherwise
>> @@ -1813,7 +1804,7 @@ static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
>> return NULL;
>>
>> plist_for_each_entry(p, head, pushable_tasks) {
>> - if (pick_rt_task(rq, p, cpu))
>> + if (task_is_pushable(rq, p, cpu) == 1)
>> return p;
>> }
>>
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 2d41ebe200c7..e46f69ba9ba2 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -3490,6 +3490,16 @@ void move_queued_task_locked(struct rq *rq, struct rq *dst_rq, struct task_struc
>> set_task_cpu(task, dst_rq->cpu);
>> activate_task(dst_rq, task, 0);
>> }
>> +
>> +static inline
>> +int task_is_pushable(struct rq *rq, struct task_struct *p, int cpu)
>> +{
>> + if (!task_on_cpu(rq, p) &&
>> + cpumask_test_cpu(cpu, &p->cpus_mask))
>> + return 1;
>> +
>> + return 0;
>> +}
>> #endif
>>
>> #endif /* _KERNEL_SCHED_SCHED_H */
>> --
>> 2.45.0.rc1.225.g2a3ae87e7f-goog
>>
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