linux-kernel - Re: [PATCH v2 0/6] macros for section name cleanup

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Date:	Mon, 4 May 2009 13:42:08 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	Tim Abbott <tabbott@....edu>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	linux arch <linux-arch@...r.kernel.org>,
	Anders Kaseorg <andersk@....edu>
Subject: Re: [PATCH v2 0/6] macros for section name cleanup

On Mon, May 4, 2009 at 12:32, Tim Abbott wrote:
> On Mon, 4 May 2009, Sam Ravnborg wrote:
>> +#define RW_DATA_SECTION(page_align, readmostly_align, cache_align,
>>   inittask_align) \
>> +     . = ALIGN(PAGE_SIZE);                                           \
>> +     .data : AT(ADDR(.data) - LOAD_OFFSET) {                         \
>> +             DATA_DATA                                               \
>> +             CONSTRUCTORS                                            \
>> +             NOSAVE_DATA                                             \
>> +             PAGE_ALIGNED_DATA(page_align)                           \
>> +             READMOSTLY_DATA(readmostly_align)                       \
>> +             CACHELINE_ALIGNED_DATA(cache_align)                     \
>> +             INIT_TASK(inittask_align)                               \
>> +     }
>
> How did you pick the order of the sections here?  I would think that to
> pack the .data section efficiently, you'd want to sort by alignment
> requirements so that e.g. all the at-least-page aligned sections are
> adjacent (INIT_TASK and the page-aligned sections are separated by some
> much smaller aligments here).

if this were actually the case, there should of course be some /*
comments */ above the define explaining that the order wasnt
arbitrarily pulled like a rabbit from an orifice.  if you're
scratching your head, then there's going to be plenty more people who
never ask but treat it like untouchable voodoo.
-mike