Re: [PATCH v3 01/21] sched/cache: Introduce infrastructure for cache-aware load balancing

[Madadi Vineeth Reddy]

Hi Tim,
Thanks for the patch series.

On 11/02/26 03:48, Tim Chen wrote:
> From: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
> 
> Adds infrastructure to enable cache-aware load balancing,
> which improves cache locality by grouping tasks that share resources
> within the same cache domain. This reduces cache misses and improves
> overall data access efficiency.

[..snip..]

> +void mm_init_sched(struct mm_struct *mm,
> +		   struct sched_cache_time __percpu *_pcpu_sched)
> +{
> +	unsigned long epoch;
> +	int i;
> +
> +	for_each_possible_cpu(i) {
> +		struct sched_cache_time *pcpu_sched = per_cpu_ptr(_pcpu_sched, i);
> +		struct rq *rq = cpu_rq(i);
> +
> +		pcpu_sched->runtime = 0;
> +		pcpu_sched->epoch = rq->cpu_epoch;
> +		epoch = rq->cpu_epoch;

Shouldn't cpu_epoch be read under cpu_epoch_lock, similar to how fraction_mm_sched()
and __update_mm_sched() acquire the lock before accessing this field?

Thanks,
Vineeth

> +	}
> +
> +	raw_spin_lock_init(&mm->sc_stat.lock);
> +	mm->sc_stat.epoch = epoch;
> +	mm->sc_stat.cpu = -1;
> +
> +	/*
> +	 * The update to mm->sc_stat should not be reordered
> +	 * before initialization to mm's other fields, in case
> +	 * the readers may get invalid mm_sched_epoch, etc.
> +	 */
> +	smp_store_release(&mm->sc_stat.pcpu_sched, _pcpu_sched);
> +}

[..snip..]