Re: [9fans] Inducing artificial latency

[David Leimbach <leimy2k@gmail.com>]

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On Tue, Jun 15, 2010 at 2:39 PM, erik quanstrom <quanstro@quanstro.net>wrote:

> > I've come up with a basic idea, but before I go diving in I want to
> > run it by 9fans and get opinions. What I'm thinking is writing a
> > synthetic file system that will collect writes to /net; to simulate a
> > high-latency file copy, you would run this synthetic fs, then do "9fs
> > remote; cp /n/remote/somefile .". If it's a control message, that gets
> > sent to the file immediately, but if it's a data write, that data
> > actually gets held in a queue until some amount of time (say 50ms) has
> > passed, to simulate network lag. After that time is up, the fs writes
> > to the underlying file, the data goes out, etc.
>
> instead, why don't you create a simulated ethernet device
> that adds in a delay before sending the packet along to a
> real ethernet device.
>
> the only trick will be getting the simulated ethernet to
> grab the real ethernet during setup.  i imagine that you'll
> need something like
>        ether0=type=fake
>        fake=real=#l1/ether1 i=10 iσ=20 o=5 oσ=0
> in plan9.ini
>
> - erik
>
> Could one write a filesystem server that is a passthrough to the ethernet
device instead, adding latency? Or is this really going to need to be a new
device?

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