[Python-Dev] PEP 410 (Decimal timestamp): the implementation is ready for a review (original) (raw)

Guido van Rossum guido at python.org
Thu Feb 16 03:39:18 CET 2012

On Wed, Feb 15, 2012 at 6:06 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

On 16/02/12 06:43, Guido van Rossum wrote:

This does not explain why microseconds aren't good enough. It seems none of the clocks involved can actually measure even relative time intervals more accurate than 100ns, and I expect that kernels don't actually keep their clock more accurate than milliseconds. I gather that modern x86 CPUs have a counter that keeps track of time down to a nanosecond or so by counting clock cycles. In principle it seems like a kernel should be able to make use of it in conjunction with other timekeeping hardware to produce nanosecond-resolution timestamps. Whether any existing kernel actually does that is another matter. It probably isn't worth the bother for things like file timestamps, where the time taken to execute the system call that modifies the file is likely to be several orders of magnitude larger.

Ironically, file timestamps are likely the only place where it matters. Read the rest of the thread.

-- --Guido van Rossum (python.org/~guido)

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