Re: [Qemu-devel] [PATCH 0/2] Optimization with AVX2 instruction

[Paolo Bonzini]

On 02/09/2015 07:40, Amit Shah wrote:
>> The buffer_find_nonzero_offset() will be called to check the zero page
>> > during live migration, it's a hot function. buffer_find_nonzero_offset()
>> > has already been optimized with SSE2 instructions, for platform that
>> > supports AVX2, we can optimize this function with AVX2 instructions and
>> > achieve about 25% performance gain.
> This should be a good improvement.  I recall Dave and I had a chat
> about this in the past too.
> 
> I've not yet reviewed the patchset, but I doubt anyone will have
> objections.  I'll review this shortly.

I think we need a better way to enable it than a configure option,
however.  AVX2 machines are rare, and no one would end up using it
except perhaps Gentoo or other source-based distros.

Perhaps something like the GCC ifunc attribute?

Paolo