Antonio Terceiro <[email protected]> writes: > 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.
Yeah, I guess the LAVA trend has been towards being more device-controlled (lava-test-shell and all that) and that doesn't really fit with the explicit parallelism style. Oh well. I'll get over it :-) > 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. I think on some level this model makes sense (whether it's subprocesses or threads or the dispatcher does some async stuff doesn't really matter for the mental model IMHO). > 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. I think ... perhaps both? It seems to me that the difference is around rebooting: (currently, anyway) a lava_test_shell action implies a reboot, and one thing a lava_test_shell-invoked script _cannot_ do (well, easily, there are probably hacks) is reboot. And I can just about imagine tests that might want do some configuration that requires a reboot to take effect. I think we should probably try to write some tests like my simple iperf test and see what API we would like. Here's a fun problem: devices will need to know the IP addresses of the other devices in the test. I suppose we could delay starting the lava-test-shell processes on any device until they have all booted and acquired an IP address? Or we could run some service on the host running the dispatcher that can be queried and informed of IP addresses or something. > 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. This part makes a lot of sense to me. > Are my thought too abstract for non-LAVA people? I can't answer this question :-) Cheers, mwh _______________________________________________ linaro-validation mailing list [email protected] http://lists.linaro.org/mailman/listinfo/linaro-validation
