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Date: Tue, 21 Apr 2009 20:11:41 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Robert Watson <rwatson@freebsd.org>
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
	src-committers@freebsd.org, Bruce Evans <brde@optusnet.com.au>
Subject: Re: svn commit: r191276 - in head/sys: amd64/include arm/include
 i386/include ia64/include mips/include powerpc/include sparc64/include
 sun4v/include
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On Mon, 20 Apr 2009, Robert Watson wrote:

> On Mon, 20 Apr 2009, Bruce Evans wrote:
>
>>> +#ifndef CACHE_LINE_SHIFT
>>> +#define	CACHE_LINE_SHIFT	6
>>> +#endif
>>> +#define	CACHE_LINE_SIZE		(1 << CACHE_LINE_SHIFT)
>> 
>> This still has the bogus ifdef.  Overriding the definition is difficult to 
>> do consistently even in a kernel with no modules, since CACHE_LINE_SIZE is 
>> not a kernel option.  Overriding the definition makes negative sense since 
>> the value is a maximum-maximum (possibly larger than strictly needed) so 
>> that it can be constant.
>
> OK, I've made this change.

Thanks.

> My hope is that most applications don't resort to 
> including sys/param.h and using CACHE_LINE_SIZE -- most will be able to query 
> it at run-time using interfaces we don't yet have (such as sysconf(3) and 
> some appropriate constant).  I also hope that most kernel consumers will be 
> able to use a run-time tuned version (which we also don't yet have).

You could make (have made) it __CACHE_LINE_SIZE to inhibit use.

Bruce