Well, I've used the check-the-modify-time cache trick for files in
many places (not just exmh) so some part of me certainly thinks it
is effective.  However, it occurred to me that if we do checkpoint
state, then aren't we modifying the sequences file for the current
folder on every message read?  Perhaps we look at the sequences file
more than once per message view?  Just idle speculation - we can
stick in some time calls to find out how expensive things are.
Someone asked about increasing the time resolution in the exmh log.
We could make that conditional on some support available in 8.3 -
Tcl has had "clock seconds" (like gettimeofday) and "clock clicks"
(high resolution timer) for some time.  But in 8.3 we've calibrated
clock clicks values to microseconds.  It is still only useful for
relative times, but each call to Exmh_Log could emit the microsecond
delta since the last log record.  Of course, we are measuring all
the overhead of taking the log record, etc.  I'll try it out.
> > From:  Brent Welch <welch@panasas.com>
> >  > Mh_Sequence also goes and rereads the files (.mh_sequences and the
> >  > context file) but I'm not sure how frequently that one is called.
> > In some places I maintain caches of files by checking their modify
> > but the sequence files are soo small that by the time you stat them to
> > check their date stamp, you could just read them again.
> Do you really think this is true?  I added a modify time check thinking
> it would make an improvement since we were reading it a *lot* more times
> the new code because we're trying to use the sequences.
> On the other hand, the sequences files are probably being read out of
> Even with a small file, I'd think that the time taken to do a
> [file mtime $filename] would be worth it.  My code is in proc
>   World War III:  The Wrong-Doers Vs. the Evil-Doers.

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