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Date:   Mon, 18 Oct 2021 23:00:50 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Pavel Begunkov <asml.silence@gmail.com>
Cc:     linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 2/3] block: blk_mq_rq_ctx_init cache ctx/q/hctx
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On Mon, Oct 18, 2021 at 09:37:28PM +0100, Pavel Begunkov wrote:
> We should have enough of registers in blk_mq_rq_ctx_init(), store them
> in local vars, so we don't keep reloading them.
> 
> note: keeping q->elevator may look unnecessary, but it's also used
> inside inlined blk_mq_tags_from_data().

Is this really making a difference?  I'd expect todays hyper-optimizing
compilers to not be tricked into specific register allocations just by
adding a local variable.