MPI in EDM - EDM-Project/EDM GitHub Wiki

What is MPI and Why using it in EDM

From wikipedia:

Message Passing Interface (MPI) is a standardized and portable message-passing standard designed to function on parallel computing architectures.

In EDM-Project we used open-mpi-4 which is an open-source MPI implementation [2]. MPI goals are high performance, scalability, and portability and became the "de facto standard" for communication among processes that model a parallel program running on a distributed memory system. Therefore, MPI was chosen as the suitable message fabric for EDM-Project.

MPI usage in EDM

In EDM-Project, the communication between DMS and the Client side (DM-handler & lpet) is performed by MPI. There are 3 custom typed messages:

1. RequestGetPageData:

Contains 3 fields:

  • vaddr - virtual address of the requested page.
  • Page- the content of the page in vaddr.
  • Info - request status. The values are enum typed - { new_page, error, existing_page} Usage:

Dm-handler send RequestGetPageData to DMS, and specify vaddr as the virtual address of the faulting page.

  • If the page exists in DMS's SPT, DMS copies page content to "page" and sets info=existing_page
  • If the page doesn't exist in DMS's SPT, DMS sets info=new_page
  • In any case of error, DMS sets info=error.

2. RequestEvictPageData:

Contains 3 fields:

  • vaddr - virtual address of the requested page.
  • Page- the content of the page in vaddr.
  • Info - request status. The values are enum typed - { success, fail}

Usage: lpet send RequestEvictPageDatato DMS, and specify "vaddr" as the virtual address of the page and its content in "page".

  • If DMS managed to store page in the disc, it sets info=success
  • In any case of error, DMS sets info=fail.

3. AckPage:

Contains 3 fields:

  • vaddr - virtual address.
  • error- buffer for storing error

Usage: When it is necessary to use communication with ACK, an informative error can be specified in the "error" field.

Sources:

[1] - https://en.wikipedia.org/wiki/Message_Passing_Interface - wiki page of MPI

[2] - https://github.com/open-mpi/ompi - open-mpi github repository