[PATCH] D116603: [AIX][z/OS][Support] Provide alternate mapped_file_region::dontNeedImpl implementations

[David Tenty via Phabricator via llvm-commits]

daltenty added a comment.

> LGTM, but I would prefer if we could use  ::posix_madvise() not just on AIX. This will remove the unnecessary directive path.

However, we need to buy-in from the originator which introduced this call.

Unfortunately it sounds like there is a different semantic for glibc on Linux though (namely the kernel is allowed to immediately discard dirty pages, which is why we assert the readonly property I assume), so the POSIX version is a no-op there, so we can't really unify the paths or we'll break the original behaviour. Worse, looking at the trace AIX I think we also don't make the system call, so I think we may need to abandon `posix_madvise`.


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  https://reviews.llvm.org/D116603/new/

https://reviews.llvm.org/D116603