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

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Message-ID: <CAMuHMdVTxDLnnVE0S7VfGKNB1EPnKv_7B8rgA2c+Ub7KgZHn1A@mail.gmail.com>
Date:   Tue, 28 Feb 2017 21:15:12 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        "linux-kernel@...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 7:54 PM, Mark Brown <broonie@...nel.org> wrote:
> 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.

Given this is done during early boot, what's the probability of not having
sufficient contiguous memory?

>> 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 :)

Tada...

commit f9bdb7fdd2cac17bdc9c344b6036e6939fa087cd
Author: Markus Elfring <elfring@...rs.sourceforge.net>
Date:   Fri Jan 13 12:28:04 2017 +0100

    spi: Use kcalloc() in spi_register_board_info()

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds