WHAT: Merge the PMIx branch into the devel repo, creating a new
OPAL “lmix” framework to abstract PMI support for all RTEs.
Replace the ORTE daemon-level collectives with a new PMIx
server and update the ORTE grpcomm framework to support
server-to-server collectives
WHY: We’ve had problems dealing with variations in PMI implementations,
and need to extend the existing PMI definitions to meet exascale
requirements.
WHEN: Mon, Aug 25
WHERE: https://github.com/rhc54/ompi-svn-mirror.git
Several community members have been working on a refactoring of the current PMI support within OMPI. Although the APIs are common, Slurm and Cray implement a different range of capabilities, and package them differently. For example, Cray provides an integrated PMI-1/2 library, while Slurm separates the two and requires the user to specify the one to be used at runtime. In addition, several bugs in the Slurm implementations have caused problems requiring extra coding.
All this has led to a slew of #if’s in the PMI code and bugs when the corner-case logic for one implementation accidentally traps the other. Extending this support to other implementations would have increased this complexity to an unacceptable level.
Accordingly, we have:
* created a new OPAL “pmix” framework to abstract the PMI support, with separate components for Cray, Slurm PMI-1, and Slurm PMI-2 implementations.
* Replaced the current ORTE grpcomm daemon-based collective operation with an integrated PMIx server, and updated the grpcomm APIs to provide more flexible, multi-algorithm support for collective operations. At this time, only the xcast and allgather operations are supported.
* Replaced the current global collective id with a signature based on the names of the participating procs. The allows an unlimited number of collectives to be executed by any group of processes, subject to the requirement that only one collective can be active at a time for a unique combination of procs. Note that a proc can be involved in any number of simultaneous collectives - it is the specific combination of procs that is subject to the constraint
* removed the prior OMPI/OPAL modex code
* added new macros for executing modex send/recv to simplify use of the new APIs. The send macros allow the caller to specify whether or not the BTL supports async modex operations - if so, then the non-blocking “fence” operation is used, if the active PMIx component supports it. Otherwise, the default is a full blocking modex exchange as we currently perform.
* retained the current flag that directs us to use a blocking fence operation, but only to retrieve data upon demand
This commit was SVN r32570.
(a) default binding policy is in effect. In this case, we will emit a
warning and default to not binding unless the user provided the
"oversubscribe" or "overload" modifier to the "bind-to" option.
(b) user-specified binding policy is in effect. In this case, we will
error out unless the user provided the "oversubscribe" or "overload"
modifier to the "bind-to" option as we cannot meet the directive.
Either "bind-to" modifier (oversubscribe or overload) will be accepted for
now - in 1.9, we will deprecate the "overload" term in favor of
"oversubscribe".
Also added the ability to accept a --bind-to modifier without specifying the binding policy itself so a user can specify overload-allowed with the default policy.
Closes trac:4345
cmr=v1.8.2:reviewer=rhc:subject=resolve handling of overload conditions
This commit was SVN r32005.
The following Trac tickets were found above:
Ticket 4345 --> https://svn.open-mpi.org/trac/ompi/ticket/4345
* allow users to specify just a modifier for map-by instead of requiring that they also specify a policy. Thus, we now accept --map-by :pe=3 as indicating that we should use the default mapping policy, but bind 3 cpus/proc.
* if users specify a pe's/proc but no policy, default to --map-by NUMA to ensure we have access to multiple cpus for the request. This won't guarantee we have access to enough to meet the request, but gives us a chance. In addition, we know that binding a proc to multiple cpus will work best if those cpus are all in the same NUMA, so this provides some degree of optimized behavior.
Per a request from Jeff, define "oversubscribe" for binding as a synonym for the "overload" modifier.
cmr=v1.8.2:reviewer=rhc
This commit was SVN r31967.
Refs trac:4117. Please use this commit rather than the patch attached to
the ticket; the patch had a few mistakes in the tweaked wording.
This commit was SVN r30362.
The following SVN revision numbers were found above:
r30298 --> open-mpi/ompi@58479399c3
The following Trac tickets were found above:
Ticket 4117 --> https://svn.open-mpi.org/trac/ompi/ticket/4117
Fix comm_spawn on a single host - with the new default mapping scheme, we were incorrectly computing the number of procs to put on the node.
Refs trac:4003
This commit was SVN r30033.
The following Trac tickets were found above:
Ticket 4003 --> https://svn.open-mpi.org/trac/ompi/ticket/4003
Reset topology usage for each node as we bind as multiple nodes may be linked to the same topology object. This will need to be revisited for scale as it does take some non-zero time to reset the usage each iteration. However, storing individual topology objects for every node consumes memory, so it's a tradeoff.
cmr=v1.7.4:reviewer=jsquyres:subject=Eliminate excessive binding/memory warnings
This commit was SVN r29978.
* default to bind-to core
* map-by slot if np=2
* map-by socket (balance across sockets on each node) if np > 2
* map-by <obj> will imply rank-by <obj> by default (leave default binding as above)
Fix a bug in the map-by <obj> mapper where we incorrectly compute the #procs to assign if the #slots > #procs
cmr=v1.7.4:reviewer=jsquyres:subject=Update default binding and mapping values
This commit was SVN r29919.
This change contains a non-mandatory modification
of the MPI-RTE interface. Anyone wishing to support
coprocessors such as the Xeon Phi may wish to add
the required definition and underlying support
****************************************************************
Add locality support for coprocessors such as the Intel Xeon Phi.
Detecting that we are on a coprocessor inside of a host node isn't straightforward. There are no good "hooks" provided for programmatically detecting that "we are on a coprocessor running its own OS", and the ORTE daemon just thinks it is on another node. However, in order to properly use the Phi's public interface for MPI transport, it is necessary that the daemon detect that it is colocated with procs on the host.
So we have to split the locality to separately record "on the same host" vs "on the same board". We already have the board-level locality flag, but not quite enough flexibility to handle this use-case. Thus, do the following:
1. add OPAL_PROC_ON_HOST flag to indicate we share a host, but not necessarily the same board
2. modify OPAL_PROC_ON_NODE to indicate we share both a host AND the same board. Note that we have to modify the OPAL_PROC_ON_LOCAL_NODE macro to explicitly check both conditions
3. add support in opal/mca/hwloc/base/hwloc_base_util.c for the host to check for coprocessors, and for daemons to check to see if they are on a coprocessor. The former is done via hwloc, but support for the latter is not yet provided by hwloc. So the code for detecting we are on a coprocessor currently is Xeon Phi specific - hopefully, we will find more generic methods in the future.
4. modify the orted and the hnp startup so they check for coprocessors and to see if they are on a coprocessor, and have the orteds pass that info back in their callback message. Automatically detect that coprocessors have been found and identify which coprocessors are on which hosts. Note that this algo isn't scalable at the moment - this will hopefully be improved over time.
5. modify the ompi proc locality detection function to look for coprocessor host info IF the OMPI_RTE_HOST_ID database key has been defined. RTE's that choose not to provide this support do not have to do anything - the associated code will simply be ignored.
6. include some cleanup of the hwloc open/close code so it conforms to how we did things in other frameworks (e.g., having a single "frame" file instead of open/close). Also, fix the locality flags - e.g., being on the same node means you must also be on the same cluster/cu, so ensure those flags are also set.
cmr:v1.7.4:reviewer=hjelmn
This commit was SVN r29435.
