Re: [PATCH] zram: constify attribute_group structures.

From	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] zram: constify attribute_group structures.
Date	2017-07-03 14:10 +0200
Message-ID	<tZ8kW-1aZ-3@gated-at.bofh.it> (permalink)
References	<tZ2Sf-5BT-11@gated-at.bofh.it> <tZ5wL-7r5-31@gated-at.bofh.it> <tZ6VS-5S-25@gated-at.bofh.it>
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On (07/03/17 16:00), Arvind Yadav wrote:
> On Monday 03 July 2017 02:30 PM, Sergey Senozhatsky wrote:
> > On (07/03/17 11:43), Arvind Yadav wrote:
> > > attribute_groups are not supposed to change at runtime. All functions
> > > working with attribute_groups provided by <linux/sysfs.h> work with const
> > > attribute_group. So mark the non-const structs as const.
> > > 
> > > File size before:
> > >     text	   data	    bss	    dec	    hex	filename
> > >     8293	    841	      4	   9138	   23b2	drivers/block/zram/zram_drv.o
> > > 
> > > File size After adding 'const':
> > >     text	   data	    bss	    dec	    hex	filename
> > >     8357	    777	      4	   9138	   23b2	drivers/block/zram/zram_drv.o
> > sorry, what exactly is the improvement here?
> > we grew .text bigger, why should we be happy about it?
> Yes, .text size is increased but .data size got decreased.
> Overall size will be same. the text segment is often read-only,
> to prevent a program from accidentally modifying its instructions.

well, to the best of my knowledge, nothing in C standard guarantees
that a variable with a C keyword 'const' will be placed into .text
or .rodata. not even sure if all gcc versions have the same opinion
on this.

but ok, we can move that struct to one of the RO sections (up to the
compiler to decide).

	-ss

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[PATCH] zram: constify attribute_group structures. Arvind Yadav <arvind.yadav.cs@gmail.com> - 2017-07-03 08:20 +0200
  Re: [PATCH] zram: constify attribute_group structures. Minchan Kim <minchan@kernel.org> - 2017-07-03 08:30 +0200
    Re: [PATCH] zram: constify attribute_group structures. Arvind Yadav <arvind.yadav.cs@gmail.com> - 2017-07-03 09:20 +0200
  Re: [PATCH] zram: constify attribute_group structures. Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-07-03 11:10 +0200
    Re: [PATCH] zram: constify attribute_group structures. Arvind Yadav <arvind.yadav.cs@gmail.com> - 2017-07-03 12:40 +0200
      Re: [PATCH] zram: constify attribute_group structures. Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-07-03 14:10 +0200

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