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

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Message-ID: <c85898de-0780-4690-adfa-99332eae0090@kernel.dk>
Date: Tue, 23 Jan 2024 08:58:48 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Christoph Hellwig <hch@...radead.org>, Qais Yousef <qyousef@...alina.io>
Cc: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>, 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>,
 Bart Van Assche <bvanassche@....org>
Subject: Re: [PATCH] block/blk-mq: Don't complete locally if capacities are
 different

On 1/23/24 1:47 AM, Christoph Hellwig wrote:
> On Mon, Jan 22, 2024 at 10:42:20PM +0000, Qais Yousef wrote:
>> The logic in blk_mq_complete_need_ipi() assumes SMP systems where all
>> CPUs have equal capacities
> 
> What is a capacity here?

It seems to be the chosen word to describe the performance potential of
the core in question, we use it elsewhere in the kernel. But yes, could
do with a bit more of an explanation.

>> +	return arch_scale_cpu_capacity(this_cpu) >= arch_scale_cpu_capacity(that_cpu);
> 
> oerly long line here.
> 
> Also pleas split patches for different subsystems.

Yes please, the sched/topology thing should be a separate prep patch.

-- 
Jens Axboe