linux-kernel - Re: [PATCH 2/4] block/part_stat: use __this_cpu_add() instead of access by smp_processor

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Message-ID: <20200504151052.GA25279@infradead.org>
Date:   Mon, 4 May 2020 08:10:52 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     Christoph Hellwig <hch@...radead.org>,
        linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>, Christoph Lameter <cl@...ux.com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/4] block/part_stat: use __this_cpu_add() instead of
 access by smp_processor_id()

On Mon, May 04, 2020 at 06:02:28PM +0300, Konstantin Khlebnikov wrote:
> Then all per-cpu macro should work as is for UP case too.
> Surprisingly arrow operator (struct->filed) works for arrays too =)
> 
> 
> Inlining per-cpu structures should be good for tiny UP systems.
> Especially if this could be done by few macro only in three places:
> definition, allocating and freeing.

Or we could just use the percpu ops always, which is what most
users do.  I never really go the UP microoptmization here.