Comment 48 for bug 635834

Sadly, in almost all cases for RPM, MAP_POPULATE for read-ahead
doesn't help much. Decompression and digest checking tend
to dominate CPU usage, and its write performance (where madvise(MADV_DONTNEED)
was the win) that tends to dominate I/O performance.

My guess is that MAP_POPULATE benefits would be mostly seen
with quicker startup for simple queries. But there's other factors,
such as redundant lookups, and the marshalling issues you
see in the callgrind, that likely make MAP_POPULATE unimportant.

But, by all means, show me the wall clock move faster ;-)