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Message Queue Dumping

Message Queue Dumping. MPI Side Document. History. MPIR and MQD were designed around 1995 MPIR: Process discovery Formally described in the MPIR document in 2010 MQD details were omitted MQD: Message Queue Dumping Many MPI implementations support it and almost all debuggers use it

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Message Queue Dumping

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  1. Message Queue Dumping MPI Side Document

  2. History • MPIR and MQD were designed around 1995 • MPIR: Process discovery • Formally described in the MPIR document in 2010 • MQD details were omitted • MQD: Message Queue Dumping • Many MPI implementations support it and almost all debuggers use it • Not yet documented

  3. The MQD document • V1.0: Documenting existing interface and practice • Vnext: • Merge with the MPIR document to be one side document • Introduce handle introspection interface • Other improvements

  4. Message Queue Dumping Interface • Tools and Debuggers use MQD to extract information about messages • Practically, only debuggers (need symbols) • Typically there are three conceptual queues: • Unexpected Receive • Posted Receive • Send • The MQD allows the following • Querying if MQD is supported • If yes, allows for iterating over active communicators. • Within each communicator, allows for iterating over each message

  5. Terms and Definitions • DLL: An overloaded term that refers to either: dynamic-link library, dynamically loaded library, dynamic shared object file • Image file: An executable or a shared library • May contain symbols necessary for MQD • MPI Process: An OS process that is part of the MPI application. • MPI standard does not require OS process. It’s debuggers’ requirement. • mqs_image: abtract concepts that represents collection of image files • Loaded into the process address space • Can change/relocate during runtime • Host: Where we run the debuggers • Target: Where the MPI process resides

  6. MQD DLL • Provided by the MPI implementation • Debugger does not need to know the internal implementation • Dynamically loaded by the debugger • Found by: value of MPIR_dll_name symbol in the process • Invoke debugger’s provided functionalities through tables of callbacks • Debugger calls routine from the MQD DLL during setup to provide cb’s • This allows the debug DLL to work with any MQD-complaint debugger

  7. Debugger/Debug DLL interaction • See document

  8. What’s next • Can’t just put MQD at the end of MPIR – Need to merge them in a way that makes sense • Handle introspection interface • MPIR_dll_name is not sufficient • 64-bit MPI process has compiled with MPIR_dll_name pointing to 64-bit debug DLL. 32-bit debugger needs to load 32-bit DLL! • Resource management for MPIR • How to know if we’re launched under srun, apprun, mpirun. • What is the job number, etc. • Connectivity information (what are the state of the connection between MPI processes)

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