linux-kernel - Re: [PATCH v2 2/2] block/blk-mq: Don't complete locally if capacities are different

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Date: Fri, 23 Feb 2024 08:09:17 -0800
From: Bart Van Assche <bvanassche@....org>
To: Qais Yousef <qyousef@...alina.io>, Jens Axboe <axboe@...nel.dk>,
 Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>
Cc: linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
 Sudeep Holla <sudeep.holla@....com>, Wei Wang <wvw@...gle.com>,
 Jaegeuk Kim <jaegeuk@...nel.org>, Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v2 2/2] block/blk-mq: Don't complete locally if capacities
 are different

On 2/23/24 07:57, Qais Yousef wrote:
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 2dc01551e27c..ea69047e12f7 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1167,10 +1167,11 @@ static inline bool blk_mq_complete_need_ipi(struct request *rq)
>   	if (force_irqthreads())
>   		return false;
>   
> -	/* same CPU or cache domain?  Complete locally */
> +	/* same CPU or cache domain and capacity?  Complete locally */
>   	if (cpu == rq->mq_ctx->cpu ||
>   	    (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags) &&
> -	     cpus_share_cache(cpu, rq->mq_ctx->cpu)))
> +	     cpus_share_cache(cpu, rq->mq_ctx->cpu) &&
> +	     cpus_equal_capacity(cpu, rq->mq_ctx->cpu)))
>   		return false;
>   
>   	/* don't try to IPI to an offline CPU */

I think it's worth mentioning that this change is intended for storage
controllers that only support a single completion interrupt. Anyway:

Reviewed-by: Bart Van Assche <bvanassche@....org>