[libc/string] State of PAGE_COPY_FWD / PAGE_COPY_THRESHOLD

[Florian Weimer]

On 11/01/2016 10:28 AM, Maxim Kuvyrkov wrote:
> I wanted to check performance impact of using linux zero page sharing in calls to memset (PTR, 0, SIZE).  I remembered seeing PAGE_COPY_FWD_MAYBE and PAGE_COPY_THRESHOLD in string/memcpy.c, and my plan was to copy this logic to an experimental memset() implementation.
>
> Closer inspection of the current code showed that only Mach port attempted to use full-page copying in memcpy.c, but now even the Mach port disables it.  The net result is that code in string/memcpy.c, as well as parts of headers sysdeps/generic/pagecopy.h and sysdeps/generic/memcopy.h are dead code.

I posted a patch to remove this, but it got stalled.

The Mach port no longer compiles on the master branch, so I don't know 
how we can make changes to it.

Florian