> Athlon docs recommend inlining for less than 25 machine instructions.
>
> $ objdump -d vmlinux | grep memcpy -- | wc
> 430 3709 28419
>
> so inlining them would cost 412*110 or 45k.
>
> Who is the author/maintainer of the Athlon code? I don't see any reference in the source
> or the kernel docs.
I am. Take a K7 and some benchmarking tools like lmbench and give it a whirl.
Im pretty sure you want to inline small copies. Note that we have a suprisingly
high proportion of short copies and that those we want to inline via rep movs
The inline code you want is something like
in_irq ?
jmp #1
len < 256
jmp #1
jmp out_of_line_copy
#1
[existing x86 rep based copy]
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