From: Pavel Begunkov <asml.silence@gmail.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH 2/3] block: blk_mq_rq_ctx_init cache ctx/q/hctx
Date: Tue, 19 Oct 2021 11:38:37 +0100 [thread overview]
Message-ID: <6e21b434-832f-a2c4-505e-6a9f511f578e@gmail.com> (raw)
In-Reply-To: <YW5fEpG+4G9XNuzy@infradead.org>
On 10/19/21 07:00, Christoph Hellwig wrote:
> 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.
Looking again, there are only reads before the use site, so indeed
shouldn't matter. Was left from first versions of the patch where
it wasn't the case.
--
Pavel Begunkov
next prev parent reply other threads:[~2021-10-19 10:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 20:37 [PATCH 0/3] blk_mq_rq_ctx_init() optimisations Pavel Begunkov
2021-10-18 20:37 ` [PATCH 1/3] block: skip elevator fields init for non-elv queue Pavel Begunkov
2021-10-18 20:37 ` [PATCH 2/3] block: blk_mq_rq_ctx_init cache ctx/q/hctx Pavel Begunkov
2021-10-19 6:00 ` Christoph Hellwig
2021-10-19 10:38 ` Pavel Begunkov [this message]
2021-10-18 20:37 ` [PATCH 3/3] block: cache rq_flags inside blk_mq_rq_ctx_init() Pavel Begunkov
2021-10-18 21:42 ` [PATCH 0/3] blk_mq_rq_ctx_init() optimisations Jens Axboe
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