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Re: [Qemu-devel] [PATCH v3 0/9] Improve buffer_is_zero
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 0/9] Improve buffer_is_zero |
Date: |
Tue, 30 Aug 2016 13:48:48 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 |
On 29/08/2016 20:46, Richard Henderson wrote:
> Changes from v2 to v3:
>
> * Unit testing. This includes having x86 attempt all versions of
> the accelerator that will run on the hardware. Thus an avx2 host
> will run the basic test 5 times (1.5sec on my laptop).
>
> * Drop the ppc and aarch64 specializations. I have improved the
> basic integer version to the point that those vectorized versions
> are not a win.
>
> In the case of my aarch64 mustang, the integer version is 4 times
> faster than the neon version that I delete. With effort I was
> able to rewrite the neon version to come to within a factor of 1.1,
> but it remained slower than the integer. To be fair, gcc6 makes
> very good use of ldp, so the integer path is *also* loading 16 bytes
> per insn.
>
> I can forward my standalone aarch64 benchmark if anyone is interested.
>
> Note however that at least the avx2 acceleration is still very much
> a win, being about 3 times faster on my laptop. Of course, it's
> handling 4 times as much data per loop as the integer version, so
> one can still see the overhead caused by using vector insns.
>
> For grins I wrote an avx512 version, if someone has a skylake upon
> which to test and benchmark. That requires additional configure
> checks, so I didn't bother to include it here.
Thanks, queued for 2.8.
Paolo
- [Qemu-devel] [PATCH v3 0/9] Improve buffer_is_zero, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 3/9] cutils: Export only buffer_is_zero, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 1/9] cutils: Move buffer_is_zero and subroutines to a new file, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 4/9] cutils: Rearrange buffer_is_zero acceleration, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 9/9] cutils: Remove ppc buffer zero checking, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 8/9] cutils: Remove aarch64 buffer zero checking, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 6/9] cutils: Add generic prefetch, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 5/9] cutils: Add test for buffer_is_zero, Richard Henderson, 2016/08/29
- [Qemu-devel] [PATCH v3 7/9] cutils: Rewrite x86 buffer zero checking, Richard Henderson, 2016/08/29
- Re: [Qemu-devel] [PATCH v3 0/9] Improve buffer_is_zero,
Paolo Bonzini <=