I'm not clear what level you propose this at - the BMI interface, or the
interface to the BMI method (internal to BMI). I'm not wild about
changing the BMI interface, particularly to use callbacks. While these
may seem superior to some of us, they are more complex and it really
starts to mess with the extensibility. Changes within BMI aren't a
concern. By the same light, the CONTEXT method seems a bit much.
Walt
Sam Lang wrote:
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
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