[Omp] distributed shared memory ??

[Greg Bronevetsky]

> I would like to know about memory management of software distributed
> shared memory . And I have a doub that It use memory space of all
> cluster nodes or it use only memory space of one node ?
>  
   The short story on that is that every process believes that it has
access to everybody's memory, meaning that it has a regions on its virtual
address space for every other process' memory. It can create pointers that
refer to those "remote" regions of its address space and dereference them.
Normally, if a process dereferences a pointer to a part of its address
space that hasn't yet been mmapp-ed, it gets a segmentation fault.
However, distributed shared memory systems override the segmentation fault
handler and instead of crashing, copy the page in question from the
appropriate remote process into our process' address space. Ultimately,
you can think of the whole thing as a coherent cache (it works very much
like one), except that its implementated using segmentation fault handlers
rather than real hardware. Also, it works at page granularity, rather than
cache line granularity.

                             Greg Bronevetsky