Re: [Qemu-devel] [PATCHv4 5/9] migration: search for zero instead of dup pages

[Eric Blake]

On 03/22/2013 06:46 AM, Peter Lieven wrote:
> virtually all dup pages are zero pages. remove
> the special is_dup_page() function and use the
> optimized buffer_find_nonzero_offset() function
> instead.
> 
> here buffer_find_nonzero_offset() is used directly
> to avoid the unnecssary additional checks in
> buffer_is_zero().
> 
> raw performace gain checking zeroed memory
> over is_dup_page() is approx. 15-20% with SSE2.
> 
> Signed-off-by: Peter Lieven <address@hidden>
> ---
>  arch_init.c |   21 ++++++---------------
>  1 file changed, 6 insertions(+), 15 deletions(-)

Reviewed-by: Eric Blake <address@hidden>

The code is sound, but I agree with Paolo's assessment that seeing a bit
more benchmarking, such as on non-SSE2 seupts, wouldn't hurt.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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