On Wed, Feb 20, 2013 at 07:56:26PM +1300, Michael Hudson-Doyle wrote: > [be wary of the cross post when replying!] > > Hi all, > > Seeing as LAVA isn't going to support multi-node tests or highbank in > the super near future, I spent a while today hacking up a script to run > some tests automatically on the calxeda nodes in the lab. You can see > it in all its gory detail here: > > http://bazaar.launchpad.net/~mwhudson/+junk/highbank-bench-scripts/view/head:/iperf.py > > (probably best read from the bottom up, come to think of it) > > To do things like power cycle and prepare instances in parallel, it's > written in an asynchronous style using the Twisted event-driven > framework. This was a bit of an experiment and I'm not sure what I > think of the result -- it's /reasonably/ clear and it works, but perhaps > just using one thread per node being tested and writing blocking code > (and using semaphores or whatever to synchronize) would have been > clearer. So I guess before I do any more hacking like this, it would be > good to hear what you guys (especially Ard I suppose!) think of this > style. > > In general, how to express a job that consists of a number of steps, > some of which can be executed in parallel and some of which have > dependencies is an interesting one. I suppose my eventy one is more on > the side of one-step-at-a-time by default with explicit parallelization > and threads + locks would be more on the side of parallel by default and > explicit serialization. This has implications for how we write the job > descriptions we give to a hypothetical multi-node test supporting LAVA > -- has anyone thought about this yet? I think I prefer the explicit > parallelism style myself (makes me think of cilk and grand central > dispatch and csp...).
My thoughts, from a LAVA standpoint. This parallelism style is indeed very elegant, but I couldn't think of how we could take advantage of that in the existing LAVA infrastructure. Maybe we could make the dispatcher spawn child dispatchers (one for each node involved in the test) and wait for all of them to finish. Inside each child dispatcher invocation, there should be a primitive that says "wait until all by test budies are ready" so that after flashing and booting each once can perform its setup steps (i.e. the stuff we do before actually running tests), and wait for the others before executing its part in the distributed job. This communication might be coordinated by the "parent" dispatcher through signals. I'm not sure whether this primitive would be a new dispatcher action (and thus declared in the job description file), or a binary inside the target (and thus able to be invoked from inside lava test-shell-test test runs), or both. To describe the tests, I thought of adding a new alternative attribute to the job description called "device_group", mutually exclusive with "device_type". This description would include a list of device specifications, including their type, any tags indicating special capabilities expected. We can then tag all nodes inside a single calxeda box with the same tag (say "calxeda-box-1"), then we can use that to request N devices in the same box for tests that require low-latency/high-bandwith networking between the participants. Are my thought too abstract for non-LAVA people? -- Antonio Terceiro Software Engineer - Linaro http://www.linaro.org
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