On 08/01/2018 10:15 PM, valdis.kletnieks@vt.edu wrote:
On Tue, 31 Jul 2018 15:41:28 +0200, Babis Chalios said:
I am working on the runtime system of a distributed memory programming language. For some reason we need to create a big hole on the address space of the application. We are trying to do so by using an mmap during the initialization of the runtime and then the runtime handles itself those addresses. How big a big hole, exactly? And when you say "For some reason", does that mean "For reasons I don't understand", or "For reasons I don't want to explain"? (Note that in American colloquial English, it usually means the first...) In this case it's the second case :) It's not that I don't want to explain, I just thought it was not necessary in that case.
However, we do have problems if memory overcommitment is disabled. Well, if your "big hole" plus everything already running is big enough to not fit in (RAM+SWAP), and you disable overcommit, you're going to have a bad day.... I know, that's why I m looking for alternatives.
So here goes the question: Is there any other mechanism to allow us to do what we want to? It's unclear what you're trying to *do*. Trying to re-invent MPI? If your goal is RDMA, there's already drivers available for Infiniband and other fabrics.
Indeed, I am sort of trying to re-invent MPI. So what I didn't explain before (the "for some reason" part), is that I d like to abstract MPI from the programmer using our programming model. I'd like to be able to have the "same" address space in distributed nodes. So I 'd like to pre-allocate it and then manage it by myself. The reason for doing so is that it would let me avoid address translation when I send data over. Cheers, Babis
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