linux-kernel - Re: [PATCH v2 2/3] spi: allocate spi_board

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Message-ID: <20170228185455.mdmvuc232chlveve@sirena.org.uk>
Date:   Tue, 28 Feb 2017 18:54:55 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] spi: allocate spi_board_info entries one by one

On Tue, Feb 28, 2017 at 10:24:17AM -0800, Dmitry Torokhov wrote:
> On Tue, Feb 28, 2017 at 09:16:50AM +0000, Mark Brown wrote:
> > On Mon, Feb 27, 2017 at 08:18:56PM -0800, Dmitry Torokhov wrote:
> > > Lists of spi_board_info entries registered with spi_register_board_info()
> > > can be quite long; instead of forcing memory allocator find contagious

> > Do you have numbers on that?

> Hm, so the largest array seems to be in
> arch/blackfin/mach-bf537/boards/stamp.c at max of 43 entries. The new
> board info is ether 60 or 72 bytes, so we get 2 or 3K table. Not above
> page, but still could be packed I think.

Oh wow, that's impressively large.  Still not sure the optimization is
particularly worth it though, it's small change in the grand scheme of
things.  OTOH it's a small change.

> If we decide that we want to keep single chunk I'll just change the
> allocation to kcalloc. Let me know.

I'd be inclined to do that because it requires less thinking about the
value of what should be a very small optimization either way but
whatever :)

> We should probably redo patch #1 to avoid allocating empty property sets
> anyway.

Yeah.

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