[PATCH] powerpc: system call micro optimisation

[Benjamin Herrenschmidt]

On Sun, 2006-06-11 at 01:15 +1000, Anton Blanchard wrote:
> In the syscall path we currently have:
> 
>        crclr   so
>        mfcr    r9
> 
> If we shift the crclr up we can avoid a stall on some CPUs.

Can you maybe have a quick look at the vDSO's ? They might have similar
room for optimisations...

Cheers,
Ben.

> Signed-off-by: Anton Blanchard <anton at samba.org>
> ---
> 
> Index: kernel/arch/powerpc/kernel/entry_64.S
> ===================================================================
> --- kernel.orig/arch/powerpc/kernel/entry_64.S	2006-04-26 08:03:05.380651922 -0500
> +++ kernel/arch/powerpc/kernel/entry_64.S	2006-04-26 08:03:28.076523958 -0500
> @@ -59,6 +59,7 @@ system_call_common:
>  	beq-	1f
>  	ld	r1,PACAKSAVE(r13)
>  1:	std	r10,0(r1)
> +	crclr	so
>  	std	r11,_NIP(r1)
>  	std	r12,_MSR(r1)
>  	std	r0,GPR0(r1)
> @@ -77,7 +78,6 @@ system_call_common:
>  	std	r11,GPR11(r1)
>  	std	r11,GPR12(r1)
>  	std	r9,GPR13(r1)
> -	crclr	so
>  	mfcr	r9
>  	mflr	r10
>  	li	r11,0xc01
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