From: Rob Ross <[email protected]>

Should we consider this as interest in working on this problem on the IBM side :)? -- Rob

Say what?! ;) Meaning we can get rid of all o(p) allocations? Not sure how you do internal collectives on behalf of the app/mpi-io without at least some of those. I was looking more for agreement that collective i/o is 'what it is'... and maybe some idea if we just have some known limitations on scaling it. Yes, that BG alltoallv is a bigger problem that we can avoid with an env var -- is that just going to have to be 'good enough'? (I think that Jeff P wrote that on BG/P and got good performance with that alltoallv. Trading memory for performance, not unusual, and at least it's selectable.)