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Re: [Qemu-devel] [v2 0/2] add avx2 instruction optimization
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [v2 0/2] add avx2 instruction optimization |
Date: |
Thu, 7 Apr 2016 12:09:52 +0100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
* Eric Blake (address@hidden) wrote:
> 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.
I've just posted that RFE:
https://sourceware.org/bugzilla/show_bug.cgi?id=19920
Dave
> --
> Eric Blake eblake redhat com +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- Re: [Qemu-devel] [v2 0/2] add avx2 instruction optimization,
Dr. David Alan Gilbert <=