[$] Dueling memory-management performance regressions

The 2019 Linux Storage, Filesystem, andMemory-Management Summit included adetailed discussion about a memory-management fix thataddressed one performance regression while causing another. That fix,which was promptly reverted, is still believed by most memory-managementdevelopers to implement the correct behavior, so apatch posted by Andrea Arcangeli in early May has relatively broadsupport. That patch remains unapplied as of this writing, but thediscussion surrounding it has continued at a slow pace over the lastmonth. Memory-management subsystem maintainer Andrew Morton is faced witha choice: which performance regression is more important?