netdev - Re: [PATCH] realtek: rtl8xxxu: Use const init arrays

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Message-ID: <wrfjponj4xpq.fsf@redhat.com>
Date:   Sat, 01 Oct 2016 16:32:17 -0400
From:   Jes Sorensen <Jes.Sorensen@...hat.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Kalle Valo <kvalo@...eaurora.org>, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] realtek: rtl8xxxu: Use const init arrays

Joe Perches <joe@...ches.com> writes:
> On Sat, 2016-10-01 at 14:53 -0400, Jes Sorensen wrote:
>> Joe Perches <joe@...ches.com> writes:
>> > Make the init arrays const to reduce data.
>> > $ size drivers/net/wireless/realtek/rtl8xxxu/built-in.o*
>> > (allyesconfig: x86-32)
>> >    text	   data	    bss	    dec	    hex	filename
>> >   80107 13651 58 93816 16e78
>> > drivers/net/wireless/realtek/rtl8xxxu/built-in.o.new
>> >   65303 28435 58 93796 16e64
>> > drivers/net/wireless/realtek/rtl8xxxu/built-in.o.old
>> In total you grow the kernel by 20 bytes. You reduce the data segment
>> substantially while growing the text segment instead.
>
> No, not really.   The alignment boundaries move a bit for
> this particular compilation.  It could go the other way for
> a different compiler version or set of CONFIG options.
>
> What's important is multiple pages of .data move to .rodata.

Your output shows it moving to the text segment - if it's in a different
segment, eg. rodata, you should use output demonstrating that to justify
the change.

Jes