So, the plan is to put all of the hints in one long string and just pass
that string in through the create interface?
Walt
Julian Martin Kunkel wrote:
Hi,
So I think we're mostly trying to work out what our API should really
be, whether we should extend the distro functionality vs. going totally
to hints, and if we go to hints what that API should look like, right?
probably the distribution needs a function which initializes/sets the internal
parameter depending on the string. Maybe another one which fancy writes the
parameters to a char buffer.
I'm down with that. For the record, my concern over strings isn't in
our processing them - its the users having to muck with them -
especially when passing numeric data. I just worry about lots of
mallocing/string copying blech when all you really want to do is set the
stripe size to the variable x.
I think extra mallocing is not really necessary only once to generate the
string which can be generated with snprintf the string could look
like "ioservercount=2;ioservers=node1,node4;dist=simplestripe;dist_stripesize=65536"
whereas options without the prefix "dist_" may be processed by code common to
all distributions.
I do not see the benefit of putting the responsibility of server mapping to
the distribution right now (maybe for raid ?). I like outsourced/common
processing which is done in the create sm right now.
I personally don't think the environment variable approach is all that
useful for PVFS. I believe this because there are only a *very* limited
number of cases where it would apply cleanly (e.g. pvfs2-cp) that there
isn't another mechanism for doing the same thing (e.g. MPI-IO hints). I
think that MPI-IO hints should have some mechanism along those lines,
and I wouldn't mind discussing that separately, but that's a different
topic.
Ok I think its true that it might not be that useful for the common case and
that MPI hints should be used.
I found it useful for testing and experimenting with PVFS and I think its no
big deal if environment processing will not be added to CVS. I will add the
functionality fitting to the new hint interface in my branch.
I don't think that I actually might be useful for implementing the new hint
mechanism because I think you have to revise the code anyway (and it won't be
so much work I guess, either), but that is no big deal.
Julian
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--
Dr. Walter B. Ligon III
Associate Professor
ECE Department
Clemson University
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