linux-kernel - Re: [PATCH] sched: Remove unnecessary initialization in init_cfs

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Message-ID: <10b8fc5b-fa72-4772-939b-7b43b7861eca@linux.alibaba.com>
Date: Tue, 5 Nov 2024 09:21:23 +0800
From: yaoma <yaoma@...ux.alibaba.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: Remove unnecessary initialization in
 init_cfs_bandwidth() function



在 2024/11/4 20:18, Peter Zijlstra 写道:
> On Mon, Nov 04, 2024 at 08:14:43PM +0800, Bitao Hu wrote:
>> The root task group is statically defined, and non-root task groups
>> are allocated memory using kmem_cache_alloc() with the __GFP_ZERO
>> flag. In both cases, the corresponding 'struct cfs_bandwidth' is a
>> block of all-zero memory. Therefore, it is unnecessary to explicitly
>> set zeros in the init_cfs_bandwidth() function.
>>
>> Signed-off-by: Bitao Hu <yaoma@...ux.alibaba.com>
>> ---
>>   kernel/sched/fair.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 2d16c8545c71..2fd96641164f 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -6573,10 +6573,8 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
>>   void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth *parent)
>>   {
>>   	raw_spin_lock_init(&cfs_b->lock);
>> -	cfs_b->runtime = 0;
>>   	cfs_b->quota = RUNTIME_INF;
>>   	cfs_b->period = ns_to_ktime(default_cfs_period());
>> -	cfs_b->burst = 0;
>>   	cfs_b->hierarchical_quota = parent ? parent->hierarchical_quota : RUNTIME_INF;
>>   
>>   	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
> 
> But this shows someone thought about it and 0 is the right value, and
> not an oversight.

Okay, I got it.