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Subject: Re: [PATCH] [RFC] [2.5 i386] GCC 3.1 -march support, PPRO_FENCE
	reduction, prefetch fixes and other CPU-related changes
From: Luca Barbieri <ldb@ldb.ods.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: "J.A. Magallon" <jamagallon@able.es>,
       Linux-Kernel ML <linux-kernel@vger.kernel.org>
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On Sun, 2002-08-04 at 23:54, Alan Cox wrote:
> On Sun, 2002-08-04 at 21:23, Luca Barbieri wrote:
> > Added, with the exception that sfence is only used if CONFIG_X86_OOSTORE
> > is not defined (currently never).
> 
> Ok sorry I follow what you are doing. What I don't understand is why you
> are generating unneeded sfence/mfence instructions in the other cases ?
It was my fault: I explained it incorrectly. sfence is only used if both
CONFIG_X86_OOSTORE and CONFIG_MMXEXT are set, which currently never
happens with the existing processors.
 
> When we use MMX/SSE we need the view to be consistent anyway so the
> various copying routines already handle this internally. 
That's why sfence is not used unless CONFIG_X86_OOSTORE (and
CONFIG_X86_MMXEXT) is defined.
mfence and lfence instead replace the "lock; addl $0,0(%%esp)". Is this
wrong?


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