[RFC] nanoseconds vs. the epoch

A preliminary patch for nanosecond timestamps is underway.  I consider it
useful to take (at least) the top two bits of the ns timestamp as an extension
to the seconds field, extending the unix epoch on 64-bit systems by (at least)
272 years without needing more than a 64-bit timestamp.

The unanswered question is whether we want to extend the epoch by some orders
of magnitude at the expense of resolution in the nanoseconds field?  For
example, NTFS has 100ns resolution for files and if we bumped the ext3
granularity to only 8ns we would gain 2176 years in the epoch department.

The other alternative is to be "happy enough" with the 272-year extension
for the current 128-byte inodes, keeping 1ns maximum resolution and then
worry about this when we have a 64-bit inode and allocate a larger field
for seconds (48 bits is enough for 12M years...).

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.