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From: Matthew Wilcox <willy@infradead.org>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs: optimise kiocb_set_rw_flags()
Date: Sat, 1 Aug 2020 16:37:11 +0100	[thread overview]
Message-ID: <20200801153711.GV23808@casper.infradead.org> (raw)
In-Reply-To: <e523f51f59ad6ecdad4ad22c560cb9c913e96e1a.1596277420.git.asml.silence@gmail.com>

On Sat, Aug 01, 2020 at 01:36:33PM +0300, Pavel Begunkov wrote:
> Use a local var to collect flags in kiocb_set_rw_flags(). That spares
> some memory writes and allows to replace most of the jumps with MOVEcc.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

If you want to improve the codegen here further, I would suggest that
renumbering the IOCB flags to match the RWF flags would lead to better
codegen (can't do it the other way around; RWF flags are userspace ABI,
IOCB flags are not).  iocb_flags() probably doesn't get any worse because
the IOCB_ flags don't have the same numbers as the O_ bits (which differ
by arch anyway).


  parent reply	other threads:[~2020-08-01 15:37 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-01 10:36 [PATCH] fs: optimise kiocb_set_rw_flags() Pavel Begunkov
2020-08-01 10:42 ` Pavel Begunkov
2020-08-01 15:37 ` Matthew Wilcox [this message]
2020-08-01 17:01   ` Jens Axboe
2020-08-02  8:33     ` Pavel Begunkov
2020-08-02  8:41   ` Pavel Begunkov
2020-08-01 17:02 ` Jens Axboe
2020-08-02  8:21   ` Pavel Begunkov
  -- strict thread matches above, loose matches on Subject: below --
2020-01-17  1:16 Pavel Begunkov
2020-01-17  1:21 ` Matthew Wilcox
2020-01-17  1:23   ` Pavel Begunkov

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