linux-kernel - Re: [PATCH v2] sched_ext: Replace hardcoding with macro and minor typo fix

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Message-ID: <c541c0f7-4b43-4527-9a01-ed57aa0f78b1@kylinos.cn>
Date: Fri, 15 Nov 2024 08:33:06 +0800
From: Zhao Mengmeng <zhaomengmeng@...inos.cn>
To: Tejun Heo <tj@...nel.org>, Zhao Mengmeng <zhaomzhao@....com>
Cc: void@...ifault.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched_ext: Replace hardcoding with macro and minor
 typo fix

On 2024/11/15 01:12, Tejun Heo wrote:
> Hello,
> 
> On Wed, Nov 13, 2024 at 10:59:08AM +0800, Zhao Mengmeng wrote:
>> From: Zhao Mengmeng <zhaomengmeng@...inos.cn>
>>
>> 1. replace hardcoding with SCX_KF_UNLOCKED.
>> 2. scx_next_task_picked() has been replaced with siwtch_class().
>> 3. minor typo fixes.
>>
>> Signed-off-by: Zhao Mengmeng <zhaomengmeng@...inos.cn>
>> ---
>>  kernel/sched/ext.c             | 6 +++---
>>  tools/sched_ext/scx_qmap.bpf.c | 2 +-
>>  2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
>> index 1b1c33f12dd7..832f77d1d318 100644
>> --- a/kernel/sched/ext.c
>> +++ b/kernel/sched/ext.c
>> @@ -2759,10 +2759,10 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
>>  		 * If the previous sched_class for the current CPU was not SCX,
>>  		 * notify the BPF scheduler that it again has control of the
>>  		 * core. This callback complements ->cpu_release(), which is
>> -		 * emitted in scx_next_task_picked().
>> +		 * emitted in switch_class().
>>  		 */
>>  		if (SCX_HAS_OP(cpu_acquire))
>> -			SCX_CALL_OP(0, cpu_acquire, cpu_of(rq), NULL);
>> +			SCX_CALL_OP(SCX_KF_UNLOCKED, cpu_acquire, cpu_of(rq), NULL);
> 
> I think this is actually a bug. David, shouldn't this be SCX_KF_REST?
> 
>>  		rq->scx.cpu_released = false;
>>  	}

Got it.
>> @@ -6096,7 +6096,7 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
>>  		if (cpu != cpu_of(this_rq)) {
>>  			/*
>>  			 * Pairs with smp_store_release() issued by this CPU in
>> -			 * scx_next_task_picked() on the resched path.
>> +			 * switch_class() on the resched path.
>>  			 *
>>  			 * We busy-wait here to guarantee that no other task can
>>  			 * be scheduled on our core before the target CPU has
>> diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
>> index ee264947e0c3..f230641929ec 100644
>> --- a/tools/sched_ext/scx_qmap.bpf.c
>> +++ b/tools/sched_ext/scx_qmap.bpf.c
>> @@ -5,7 +5,7 @@
>>   * There are five FIFOs implemented using BPF_MAP_TYPE_QUEUE. A task gets
>>   * assigned to one depending on its compound weight. Each CPU round robins
>>   * through the FIFOs and dispatches more from FIFOs with higher indices - 1 from
>> - * queue0, 2 from queue1, 4 from queue2 and so on.
>> + * queue0, 2 from queue1, 3 from queue2 and so on.
> 
> The number to dispatch is determined by:
> 
>   cpuc->dsp_cnt = 1 << cpuc->dsp_idx;
> 
> I think the existing comment is correct.

You are right, I missed something. Will send a V3