mrulist direct mode, monitoring pool servers

Eric S. Raymond esr at
Mon Apr 24 16:13:12 UTC 2017

Very old mail...

Hal Murray <hmurray at>:
> esr at said:
> >> If we can't go fast enough, we should be able to get some of the
> >> data and/or some estimates of how much we are missing.
> > Some of the data, yes.  As the Mode 6 protocol is designed I don't see how
> > to get good estimates.
> > On the other hand, I can imagine an inexpensive protocol extension that
> > would help a lot - adding a tag to the front of each span that reports the
> > MRU-list size at the time of transmission.  If your client sees this number
> > rising rather than falling during a span sequence then you can at least be
> > warned that you're probably in a losing race. 
> The size of the list isn't what you want.  If slots are getting recycled, the list size will be constant.
> I think we can get the numbers we need, not through the mru protocol but by through something like monstats.  It doesn't have what we need, but we can fix that.
> [memoryusage]
> > Can't easily see it being a big problem in the normal mode either, frankly.
> > By definition the client memory usage has to be linearly related to the
> > memory usage on the server, and even in Python I don't think the constant of
> > proportionality can be very large. I'd guess around 2x-3x. 
> The context is running on a cloud server where they charge for memory.  The server has a lot of that.  A few experiments showed that collecting needed more than was available.  I'll try to get more data if you think it's important.
> >> Any suggestions for a UI/CLI?
> > Not before seeing the patch, no.
> Current UI is a "direct" command to ntpq that sets a flag which gets passed in to the worker code which then prints each batch out on the fly.

I've lost the context of this discussion.  Is there some related thing that
still needs to be done to the MRUlist code?
		<a href="">Eric S. Raymond</a>

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