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From Dean Gaudet <dgau...@arctic.org>
Subject Re: [PATCH] shared time again
Date Tue, 05 May 1998 18:01:29 GMT


On Wed, 6 May 1998, Wan-Teh Chang wrote:

> PR_Now() returns a signed, 64-bit time, which is the number
> of microseconds since the NSPR epoch (same as the Unix epoch),
> midnight, 1 Jan 1970 UTC.  This one may not be monotonically
> increasing because the system time may be reset at any time by
> the system administrator or an NTP client/server.

Actually the full solution I intended for this involves a little help from
the kernel.  Add a /dev/calibrate which is mmappable and contains the two
constants CPUS and EPOCH (on linux there's actually a few more interesting
time calibration constants that it would contain). Then code to read
those.  That'll solve these problems.  (And solves another -- smp boxes
with out of sync time stamp counters can use different mappings for that
page without the app knowing... but it seems like boxes using the intel MP
spec are always in sync.) 

What I posted was just a hacked up test case that I'll use to figure out
if it's even worth it. 

Dean


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