From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
Subject: Re: [PATCH 4/5] io_uring: optimise out req->opcode reloading
Date: Wed, 6 Oct 2021 10:48:46 -0600 [thread overview]
Message-ID: <6dc5a0c8-ac30-e4ee-4833-74a25fac2dc9@kernel.dk> (raw)
In-Reply-To: <6ba869f5f8b7b0f991c87fdf089f0abf87cbe06b.1633532552.git.asml.silence@gmail.com>
On 10/6/21 9:06 AM, Pavel Begunkov wrote:
> Looking at the assembly, the compiler decided to reload req->opcode in
> io_op_defs[opcode].needs_file instead of one it had in a register, so
> store it in a temp variable so it can be optimised out. Also move the
> personality block later, it's better for spilling/etc. as it only
> depends on @sqe, which we're keeping anyway.
>
> By the way, zero req->opcode if it over IORING_OP_LAST, not a problem,
> at the moment but is safer.
That had me a bit worried, but you mean it's reloading req->opcode,
not sqe->opcode. Phew.
--
Jens Axboe
next prev parent reply other threads:[~2021-10-06 16:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-06 15:06 [PATCH 0/5] bunch of random cleanup for-next Pavel Begunkov
2021-10-06 15:06 ` [PATCH 1/5] io_uring: optimise plugging Pavel Begunkov
2021-10-06 15:06 ` [PATCH 2/5] io_uring: safer fallback_work free Pavel Begunkov
2021-10-06 15:06 ` [PATCH 3/5] io_uring: reshuffle io_submit_state bits Pavel Begunkov
2021-10-06 15:06 ` [PATCH 4/5] io_uring: optimise out req->opcode reloading Pavel Begunkov
2021-10-06 16:48 ` Jens Axboe [this message]
2021-10-06 15:06 ` [PATCH 5/5] io_uring: remove extra io_ring_exit_work wake up Pavel Begunkov
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