[RFC] simulating network properties for benchmarks

[Martin Pool]

On 21 Jul 2006, Aaron Bentley <aaron.bentley at utoronto.ca> wrote:
> Robert Collins wrote:
> 
> > Heres a prototype of what I was referring to. The decorator in it was
> > quick-coded, if the future directions I mention in it are to be done, it
> > would deserve unit tests, as high layer tests could no longer test it at
> > that point.
> > 
> > I'm pushing this up to
> > sftp://bazaar.launchpad.net/~bzr/bzr/test-sftp-latency now.
> 
> This is the approach seems pretty natural to me.  But an interesting
> alternative would be for the transport to not sleep, but instead, move
> the clock ahead.  That would mean we could simulate slow operations
> quickly, which would make such tests easier to run.
> 
> Obviously we can't change the system clock, but we could have the
> transport update a global variable, and have the bench suite use that
> for its calculations.

And then basically show it as e.g. "4.2s real time, 123.2s simulated
IO".  It could be nice.

> The disadvantage is that lsprof won't understand what's going on-- but
> does sleep show up in lsprof, or does it measure CPU time?

I'm not sure.   I thought it was wall time.

-- 
Martin