From: Dave Chinner <david@fromorbit.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>,
axboe@kernel.dk, agk@redhat.com, snitzer@kernel.org,
philipp.reisner@linbit.com, lars.ellenberg@linbit.com,
christoph.boehmwalder@linbit.com, hch@infradead.org,
djwong@kernel.org, minchan@kernel.org, senozhatsky@chromium.org,
patches@lists.linux.dev, linux-block@vger.kernel.org,
linux-mm@kvack.org, linux-xfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, dm-devel@redhat.com,
drbd-dev@lists.linbit.com, linux-kernel@vger.kernel.org,
hare@suse.de, p.raghav@samsung.com, da.gomez@samsung.com,
kbusch@kernel.org
Subject: Re: [PATCH 3/5] iomap: simplify iomap_init() with PAGE_SECTORS
Date: Sat, 22 Apr 2023 08:34:20 +1000 [thread overview]
Message-ID: <20230421223420.GH3223426@dread.disaster.area> (raw)
In-Reply-To: <ZEMH9h/cd9Cp1t+X@bombadil.infradead.org>
On Fri, Apr 21, 2023 at 03:02:30PM -0700, Luis Chamberlain wrote:
> On Fri, Apr 21, 2023 at 09:14:00PM +0100, Matthew Wilcox wrote:
> > On Fri, Apr 21, 2023 at 12:58:05PM -0700, Luis Chamberlain wrote:
> > > Just use the PAGE_SECTORS generic define. This produces no functional
> > > changes. While at it use left shift to simplify this even further.
> >
> > How is FOO << 2 simpler than FOO * 4?
> >
> > > - return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> > > + return bioset_init(&iomap_ioend_bioset, PAGE_SECTORS << 2,
>
> We could just do:
>
>
> - return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
> + return bioset_init(&iomap_ioend_bioset, 4 * PAGE_SECTORS,
Yes, please.
> The shift just seemed optimal if we're just going to change it.
Nope, it's just premature optimisation at the expense of
maintainability. The compiler will optimise the multiplication into
shifts if that is the fastest way to do it for the given
architecture the code is being compiled to.
-Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2023-04-21 22:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-21 19:58 [PATCH 0/5] block: simplify with PAGE_SECTORS_SHIFT Luis Chamberlain
2023-04-21 19:58 ` [PATCH 1/5] dm integrity: simplify by using PAGE_SECTORS_SHIFT Luis Chamberlain
2023-04-21 20:15 ` Matthew Wilcox
2023-04-21 19:58 ` [PATCH 2/5] drbd: use PAGE_SECTORS_SHIFT and PAGE_SECTORS Luis Chamberlain
2023-04-24 8:26 ` Christoph Böhmwalder
2023-04-21 19:58 ` [PATCH 3/5] iomap: simplify iomap_init() with PAGE_SECTORS Luis Chamberlain
2023-04-21 20:14 ` Matthew Wilcox
2023-04-21 22:02 ` Luis Chamberlain
2023-04-21 22:24 ` Jens Axboe
2023-04-21 22:30 ` Luis Chamberlain
2023-04-21 22:36 ` Jens Axboe
2023-04-21 22:34 ` Dave Chinner [this message]
2023-04-24 5:55 ` Christoph Hellwig
2023-04-21 19:58 ` [PATCH 4/5] dm bufio: simplify by using PAGE_SECTORS_SHIFT Luis Chamberlain
2023-04-21 19:58 ` [PATCH 5/5] zram: use generic PAGE_SECTORS and PAGE_SECTORS_SHIFT Luis Chamberlain
2023-04-24 2:36 ` Sergey Senozhatsky
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