> Well, by "switch" I just meant "new command line option". The obvious
form of that would be, as you say, just the ability to set the netperf
xfer size directly...

Yes. And let's remember why we're having this discussion - I asked why the 
charts for very slow links had so little granularity. RRUL has been this way 
since 2012, so it is not a "hotly-demanded" feature: we don't need to spend a 
whole lot of time on it.

Given that it's possible (when warranted) to tell netperf to increase its 
granularity, a Flent command line option would allow the person to request it 
if needed. My thoughts:

* The default for Flent should remain the same: defaults work fine for most 
people. The defaults also create datasets that are consistent with earlier test 
* The option should be named to suggest its purpose. I initially thought about 
"slow links" (because that kicked off this issue) but something along the lines 
of "increased granularity for slow links" might be better.
* The option should allow the person to specify the numbers directly (e.g. `-m 
2048,2048`) to simplify implementation.
* The documentation should describe that this is the amount of data in bytes to 
be transferred between data samples; that using a smaller number increases 
granularity at the expense of higher CPU demand and increased data file size; 
provide guidance that the default is `-m ???,???` (whatever is correct); and 
that `-m 2048,2048` works fine for links under 1mbps.
* I suspect that the presence of two numbers indicates that one is for 
transmit, the other for receive. If so, the docs should specify which is which, 
and note that using the same value for both is reasonable.
* *[NB]* I was initially confused about the `-m` option - it doesn't seem to be 
described in the netperf documentation. Perhaps we could include a side note 
stating its purpose.

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