Revert "slub: Fix calculation of cpu slabs"

Revert for now.

This reverts commit cf99027de5ff5ded9b12ee6912f5a96480a99e73.
Revert "perf: Fix mmap() accounting hole"

Revert for now.

This reverts commit bf02ed4dc06826647aa88c3bd78ba3f3b594d6e7.
Revert "perf: Fix perf mmap bugs"

Revert for now.

This reverts commit 577b8c3417351bd40f02a4ceb6bc4ba20fe371dd.