[PATCH 0/5] Added optimized memcpy/memmove/memset for A64FX

[Florian Weimer]

* Wilco Dijkstra via Libc-alpha:

> 5. Odd prefetches
>
> I have a hard time believing first prefetching the data to be
> written, then clearing it using DC ZVA (???), then prefetching the
> same data a 2nd time, before finally write the loaded data is
> helping performance...  Generally hardware prefetchers are able to
> do exactly the right thing since memcpy is trivial to prefetch.  So
> what is the performance gain of each prefetch/clear step? What is
> the difference between memcpy and memmove performance (given memmove
> doesn't do any of this)?

Another downside is exposure of latent concurrency bugs:

  G1: Phantom zeros in cardtable
  <https://bugs.openjdk.java.net/browse/JDK-8039042>

I guess the CPU's heritage is shining through here. 8-)