Merge of r3966, r3967, r3968, r3969, r3970, r3971:

Merge of r3966, r3967, r3968, r3969, r3970, r3971:

Cache loader improvements:

The cache loader performs two tasks: inserting cache objects in inactivity
list and evaluating total cache size. Reading just directory is enough for
this purpose. Elimination of reading cache files saves at least one disk I/O
operation per file.