Re: [Qemu-devel] [PATCH v2 0/8] Improve buffer_is_zero

[Daniel P. Berrange]

On Wed, Aug 24, 2016 at 10:48:27AM -0700, Richard Henderson wrote:
> Patches 1-4 remove the use of ifunc from the implementation.
> 
> Patch 6 adjusts the x86 implementation a bit more to take
> advantage of ptest (in sse4.1) and unaligned accesses (in avx1).
> 
> Patches 3 and 7 are the result of my conversation with Vijaya
> Kumar with respect to ThunderX.
> 
> Patch 8 is the result of seeing some really really horrible code
> produced for ppc64le (gcc 4.9 and mainline).
> 
> This has had limited testing.  What I don't know is the best way
> to benchmark this -- the only way I know to trigger this is via
> the console, by hand, which doesn't make for reasonable timing.
> 
> Changes v1-v2:
>   * Add patch 1, moving everything to a new file.
>   * Fix a typo or two, which had the wrong sense of zero test.
>     These had mostly beed fixed in the intermediate patches,
>     but it wouldn't have helped bisection.
> 
> 
> r~
> 
> 
> Richard Henderson (8):
>   cutils: Move buffer_is_zero and subroutines to a new file
>   cutils: Remove SPLAT macro
>   cutils: Export only buffer_is_zero
>   cutils: Rearrange buffer_is_zero acceleration
>   cutils: Add generic prefetch
>   cutils: Rewrite x86 buffer zero checking
>   cutils: Rewrite aarch64 buffer zero checking
>   cutils: Rewrite ppc buffer zero checking
> 
>  configure             |  21 +--
>  include/qemu/cutils.h |   2 -
>  migration/ram.c       |   2 +-
>  migration/rdma.c      |   5 +-
>  util/Makefile.objs    |   1 +
>  util/bufferiszero.c   | 432 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  util/cutils.c         | 244 ----------------------------
>  7 files changed, 441 insertions(+), 266 deletions(-)
>  create mode 100644 util/bufferiszero.c

Since your v1 series has a report of breaking arm64, I thnk this is a good
candidate for adding unit tests eg a tests/test-bufferiszero.c file which
exercises & validates the various codepaths.

Regards,
Daniel
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