linux-kernel - Re: [PATCH v2 2/3] sched/fair: Move hot load

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Date:	Thu, 03 Dec 2015 14:38:16 -0500
From:	Waiman Long <waiman.long@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Yuyang Du <yuyang.du@...el.com>, Paul Turner <pjt@...gle.com>,
	Ben Segall <bsegall@...gle.com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v2 2/3] sched/fair: Move hot load_avg into its own cacheline

On 12/03/2015 05:56 AM, Peter Zijlstra wrote:
> On Wed, Dec 02, 2015 at 01:41:49PM -0500, Waiman Long wrote:
>> +/*
>> + * Make sure that the task_group structure is cacheline aligned when
>> + * fair group scheduling is enabled.
>> + */
>> +#ifdef CONFIG_FAIR_GROUP_SCHED
>> +static inline struct task_group *alloc_task_group(void)
>> +{
>> +	return kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
>> +}
>> +
>> +static inline void free_task_group(struct task_group *tg)
>> +{
>> +	kmem_cache_free(task_group_cache, tg);
>> +}
>> +#else /* CONFIG_FAIR_GROUP_SCHED */
>> +static inline struct task_group *alloc_task_group(void)
>> +{
>> +	return kzalloc(sizeof(struct task_group), GFP_KERNEL);
>> +}
>> +
>> +static inline void free_task_group(struct task_group *tg)
>> +{
>> +	kfree(tg);
>> +}
>> +#endif /* CONFIG_FAIR_GROUP_SCHED */
> I think we can simply always use the kmem_cache, both slab and slub
> merge slabcaches where appropriate.

I did that as I was not sure how much overhead would the introduction of 
a new kmem_cache bring. It seems like it is not really an issue. So I am 
fine with making the kmem_cache change permanent.

Cheers,
Longman
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