[Bug libc/24872] __memmove_avx_unaligned_erms() performs significantly much slower than __memcpy_ssse3()

["hjl.tools at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=24872

--- Comment #11 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to 苟浩 from comment #10)
> I also encountered a similar problem when I used the stream tool to test the
> memory bandwidth.
> 
> On the same machine, centos7 and centos8 are installed. Centos7 uses

What is your CPU?

> glibc-2.17 and centos8 uses glibc-2.28. The stream test data shows that the
> memory performance of centos8 is much worse than that of centos7.
> 
> From the flame diagram, the only difference between the two calls is that
> glibc-2.28 uses　__memmove_avx_unaligned_erms(), glibc-2.17 uses __memcpy_
> ssse3()。
> 
> This machine is x86_64. However, under aarch64 architecture, glibc-2.17 and
> glibc-2.28 perform almost the same.
> 
> The stream compile command uses:
> 
> # gcc -O3 -mcmodel=large -fopenmp -DSTREAM_ARRAY_SIZE=2147483648 -DNTIMES=30
> stream.c -o stream

What is stream.c?

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