Hi All,
Right now if multiple methods are enabled in BMI, we tend to get poor performance from the "fast" network, because BMI_testcontext iterates through all the active methods calling testcontext for each one. It tries to be smart about which methods get scheduled ;-) to prevent starvation, but it treats all the methods fairly, which tends to make tcp (the slow one) hog the time spent in testcontext. I have a few ideas for this, so I'll go ahead and propose them and let you all shoot them down or propose others.
Option CALLBACK: Instead of returning completion as a list in testcontext, we allow a BMI context to be constructed with a callback, and on completion of operations, the callback is called. This allows each method to drive its own operations, and notify the consumer of completion immediately. There would still need to be a testcontext call for methods that only service operations during that call. The changes might not be that significant, the BMI_open_context call could just take an extra parameter that was the callback function. If the parameter is null, we just use the completion list as before.
Option CONTEXT: Require separate contexts for separate methods. This pushes the problem up to the application, probably not where it belongs, since active methods are opaque from the BMI api.
Option POLL_PLAN: Modify the construct_poll_plan function in bmi that already tries to be fair, so that its aware of the performance discrepancy between methods. Maybe it can just skip tcp every other time for example. This is probably the easiest, since it doesn't require API changes and the like.
-sam _______________________________________________ Pvfs2-developers mailing list [email protected] http://www.beowulf-underground.org/mailman/listinfo/pvfs2-developers
