Re: [Qemu-devel] [v2 0/2] add avx2 instruction optimization

[Eric Blake]

On 11/12/2015 12:56 PM, Dr. David Alan Gilbert wrote:

>> One thing I still can't understand, why the unit test in host environment 
>> shows
>> 'memcmp()' have better performance?

Have you tried running under a profiler, to see if there are hotspots or
at least get an idea of where the time is being spent?

> 
> Are you aware of any program other than QEMU that also wants to do something
> similar?  Finding whether a block of memory is zero, sounds like something
> that would be useful in lots of places, I just can't think which ones.

At least dd, cp, and probably several other utilities.  It would be nice
to post an RFE to glibc to see if they can come up with a dedicated
interface that is faster than memcmp(), although that still only helps
us when targetting a system new enough to have that interface.

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

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