linux-kernel - Re: [PATCH] skx_edac: Move a few hundred bytes to text from data using const

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Message-ID: <20160822164603.GA24307@intel.com>
Date:   Mon, 22 Aug 2016 09:46:04 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Doug Thompson <dougthompson@...ssion.com>,
        Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] skx_edac: Move a few hundred bytes to text from data
 using const

On Sun, Aug 21, 2016 at 05:02:41PM -0700, Joe Perches wrote:
> Marking arrays as const makes for smaller data.

Joe,

"a few hundred" seems to be exaggeration.

Before:
$ size drivers/edac/skx_edac.ko
   text	   data	    bss	    dec	    hex	filename
   8435	   1024	     24	   9483	   250b	drivers/edac/skx_edac.ko

After:
$ size drivers/edac/skx_edac.ko
   text    data     bss     dec     hex filename
   8531	    944	     24	   9499	   251b	drivers/edac/skx_edac.ko

so "data" was reduced by 80 bytes, but "text" went up by 96.

Net increase of 16 (perhaps because some padding for alignment???)

Making read-only data const is a good idea in general, but
do we want to do it if it *increases* kernel footprint?

-Tony