linux-kernel - Re: RFC: remove __read

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Date:	Fri, 14 Dec 2007 16:38:04 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Adrian Bunk <bunk@...nel.org>, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: RFC: remove __read_mostly

Matt Mackall a écrit :
> On Thu, Dec 13, 2007 at 11:20:44PM +0100, Adrian Bunk wrote:
>   
>> I tried the following patch with a full x86 .config [1]:
>>
>> --- a/include/asm-x86/cache.h
>> +++ b/include/asm-x86/cache.h
>> -#define __read_mostly __attribute__((__section__(".data.read_mostly")))
>> +/* #define __read_mostly __attribute__((__section__(".data.read_mostly"))) */
>>
>> The result [2,3] was:
>>
>> -rwxrwxr-x 1 bunk bunk 46607243 2007-12-13 19:50 vmlinux.old
>> -rwxrwxr-x 1 bunk bunk 46598691 2007-12-13 21:55 vmlinux
>>
>> It's not a surprise that the kernel can become bigger when __read_mostly 
>> gets used, especially in cases where __read_mostly prevents gcc 
>> optimizations.
>>
>> My question is:
>> Is there anywhere in the kernel a case where __read_mostly brings a 
>> measurable improvement or can it be removed?
>>     
>
> Yes, but perhaps we can put it under CONFIG_BASE_FULL?
>
>   
Yes, we probably can do something like that (in addition to !CONFIG_SMP)





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