Re: [9fans] Inducing artificial latency

[Skip Tavakkolian <9nut@9netics.com>]

any reason loopback(3) wont work? it has options for delay and latency.

> I'm going to be doing some work with 9P and high-latency links this
> summer and fall. I need to be able to test things over a high-latency
> network, but since I may be modifying the kernel, running stuff on
> e.g. mordor is not the best option. I have enough systems here to do
> the tests, I just need to artificially add latency between them.
>
> 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.
>
> I have not really done any networking stuff or filesystems work on
> Plan 9; thus far, I've confined myself to kernel work. I could be
> completely mistaken about how 9P and networking behave, so I'm asking
> for opinions and suggestions. For my part, I'm trying to find good
> example filesystems to read (I've been looking at gpsfs, for
> instance).
>
>
> John
> --
> "With MPI, familiarity breeds contempt. Contempt and nausea. Contempt,
> nausea, and fear. Contempt, nausea, fear, and .." -- Ron Minnich