This commit improves the injection rate and latency for RDMA
operations. This is done by the following improvements:
- If C11's _Thread_local keyword is available then always use the
same virtual device index for the same thread when using RDMA. If
the keyword is not available then attempt to use any device that
isn't already in use. The binding support is enabled by default but
can be disabled via the btl_ugni_bind_devices MCA variable.
- When posting FMA and RDMA operations always attempt to reap
completions after posting the operation. This allows us to
better balance the work of reaping completions across all
application threads.
- Limit the total number of outstanding BTE transactions. This
fixes a performance bug when using many threads.
- Split out RDMA and local SMSG completion queue sizes. The RDMA
queue size is better tuned for performance with RMA-MT.
- Split out put and get FMA limits. The old btl_ugni_fma_limit MCA
variable is deprecated. The new variable names are:
btl_ugni_fma_put_limit and btl_ugni_fma_get_limit.
- Change how post descriptors are handled. They are no longer
allocated seperately from the RDMA endpoints.
- Some cleanup to move error code out of the critical path.
- Disable the FMA sharing flag on the CDM when we detect that there
should be enough FMA descriptors for the number of virtual devices
we plan will create. If the user sets this flag we will not unset
it. This change should improve the small-message RMA performance by
~ 10%.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
This commit removes the local operation count check from the local SMSG
completion queue. This check was leading to hangs due to an undocumented
feature of the ugni library. The local SMSG CQ is used to send credit
return messages back to the sender. The ugni library never checks for
the completion itself but relying on the SMSG user to periodically
check the CQ.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
This commit updates the ugni btl to make use of multiple device
contexts to improve the multi-threaded RMA performance. This commit
contains the following:
- Cleanup the endpoint structure by removing unnecessary field. The
structure now also contains all the fields originally handled by the
common/ugni endpoint.
- Clean up the fragment allocation code to remove the need to
initialize the my_list member of the fragment structure. This
member is not initialized by the free list initializer function.
- Remove the (now unused) common/ugni component. btl/ugni no longer
need the component. common/ugni was originally split out of
btl/ugni to support bcol/ugni. As that component exists there is no
reason to keep this component.
- Create wrappers for the ugni functionality required by
btl/ugni. This was done to ease supporting multiple device
contexts. The wrappers are thread safe and currently use a spin
lock instead of a mutex. This produces better performance when
using multiple threads spread over multiple cores. In the future
this lock may be replaced by another serialization mechanism. The
wrappers are located in a new file: btl_ugni_device.h.
- Remove unnecessary device locking from serial parts of the ugni
btl. This includes the first add-procs and module finalize.
- Clean up fragment wait list code by moving enqueue into common
function.
- Expose the communication domain flags as an MCA variable. The
defaults have been updated to reflect the recommended setting for
knl and haswell.
- Avoid allocating fragments for communication with already
overloaded peers.
- Allocate RDMA endpoints dyncamically. This is needed to support
spreading RMA operations accross multiple contexts.
- Add support for spreading RMA communication over multiple ugni
device contexts. This should greatly improve the threading
performance when communicating with multiple peers. By default the
number of virtual devices depends on 1) whether
opal_using_threads() is set, 2) how many local processes are in the
job, and 3) how many bits are available in the pid. The last is
used to ensure that each CDM is created with a unique id.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
Use of the old ompi_free_list_t and ompi_free_list_item_t is
deprecated. These classes will be removed in a future commit.
This commit updates the entire code base to use opal_free_list_t and
opal_free_list_item_t.
Notes:
OMPI_FREE_LIST_*_MT -> opal_free_list_* (uses opal_using_threads ())
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
Replace temporary environment variables with a MCA
parameter for the ugni btl. A user wishing to
use the ugni btl async. progress thread needs to
set the request_progress_thread param to true.
For example, using env. variable format:
export OMPI_MCA_btl_ugni_request_progress_thread=1
The old BTL interface provided support for RDMA through the use of
the btl_prepare_src and btl_prepare_dst functions. These functions were
expected to prepare as much of the user buffer as possible for the RDMA
operation and return a descriptor. The descriptor contained segment
information on the prepared region. The btl user could then pass the
RDMA segment information to a remote peer. Once the peer received that
information it then packed it into a similar descriptor on the other
side that could then be passed into a single btl_put or btl_get
operation.
Changes:
- Removed the btl_prepare_dst function. This reflects the fact that
RDMA operations no longer depend on "prepared" descriptors.
- Removed the btl_seg_size member. There is no need to btl's to
subclass the mca_btl_base_segment_t class anymore.
...
Add more
This commit adds initial ugni thread safety support.
With this commit, sun thread tests (excepting MPI-2 RMA)
pass with various process counts and threads/process.
Also osu_latency_mt passes.
WHAT: Open our low-level communication infrastructure by moving all necessary components (btl/rcache/allocator/mpool) down in OPAL
All the components required for inter-process communications are currently deeply integrated in the OMPI layer. Several groups/institutions have express interest in having a more generic communication infrastructure, without all the OMPI layer dependencies. This communication layer should be made available at a different software level, available to all layers in the Open MPI software stack. As an example, our ORTE layer could replace the current OOB and instead use the BTL directly, gaining access to more reactive network interfaces than TCP. Similarly, external software libraries could take advantage of our highly optimized AM (active message) communication layer for their own purpose. UTK with support from Sandia, developped a version of Open MPI where the entire communication infrastucture has been moved down to OPAL (btl/rcache/allocator/mpool). Most of the moved components have been updated to match the new schema, with few exceptions (mainly BTLs where I have no way of compiling/testing them). Thus, the completion of this RFC is tied to being able to completing this move for all BTLs. For this we need help from the rest of the Open MPI community, especially those supporting some of the BTLs. A non-exhaustive list of BTLs that qualify here is: mx, portals4, scif, udapl, ugni, usnic.
This commit was SVN r32317.
