This patch introduces the logic implementing hierarchical scheduling.
First and foremost, hierarchical scheduling is off by default
To enable, use -DLIBOMP_USE_HIER_SCHED=On during CMake's configure stage.
This work is based off if the IWOMP paper:
"Workstealing and Nested Parallelism in SMP Systems"
Hierarchical scheduling is the layering of OpenMP schedules for different layers
of the memory hierarchy. One can have multiple layers between the threads and
the global iterations space. The threads will go up the hierarchy to grab
iterations, using possibly a different schedule & chunk for each layer.
[ Global iteration space (0-999) ]
(use static)
[ L1 | L1 | L1 | L1 ]
(use dynamic,1)
[ T0 T1 | T2 T3 | T4 T5 | T6 T7 ]
In the example shown above, there are 8 threads and 4 L1 caches begin targeted.
If the topology indicates that there are two threads per core, then two
consecutive threads will share the data of one L1 cache unit. This example
would have the iteration space (0-999) split statically across the four L1
caches (so the first L1 would get (0-249), the second would get (250-499), etc).
Then the threads will use a dynamic,1 schedule to grab iterations from the L1
cache units. There are currently four supported layers: L1, L2, L3, NUMA
OMP_SCHEDULE can now read a hierarchical schedule with this syntax:
OMP_SCHEDULE='EXPERIMENTAL LAYER,SCHED[,CHUNK][:LAYER,SCHED[,CHUNK]...]:SCHED,CHUNK
And OMP_SCHEDULE can still read the normal SCHED,CHUNK syntax from before
I've kept most of the hierarchical scheduling logic inside kmp_dispatch_hier.h
to try to keep it separate from the rest of the code.
Differential Revision: https://reviews.llvm.org/D47962
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@336571 91177308-0d34-0410-b5e6-96231b3b80d8
These are preliminary changes that attempt to use C++11 Atomics in the runtime.
We are expecting better portability with this change across architectures/OSes.
Here is the summary of the changes.
Most variables that need synchronization operation were converted to generic
atomic variables (std::atomic<T>). Variables that are updated with combined CAS
are packed into a single atomic variable, and partial read/write is done
through unpacking/packing
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D47903
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@336563 91177308-0d34-0410-b5e6-96231b3b80d8
implicit_task_end callbacks in nested parallel regions did not always give the
correct thread_num, since the inner parallel region may have already been
finalized.
Now, the thread_num is stored at the beginning of the implicit task and
retrieved at the end, whenever necessary.
A testcase was added as well.
Differential Revision: https://reviews.llvm.org/D46260
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@331632 91177308-0d34-0410-b5e6-96231b3b80d8
This change simplifies __kmp_expand_threads to take a single argument.
Previously, it allowed two arguments and had logic to decide on different
potential expansion sizes. However, no calls to __kmp_expand_threads in the
runtime make use of this extra logic. Thus the extra argument and logic is
removed here.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D41836
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@322204 91177308-0d34-0410-b5e6-96231b3b80d8
This change improves stability of the runtime when the application forks child
processes. Acquiring/releasing __kmp_initz_lock and __kmp_forkjoin_lock in the
atfork handlers insures that the actual fork does not occur while those two
locks are held, and __kmp_itt_reset() reverts the itt's global state to the
initial state which also initializes the mutex stored in the global state.
Some missing initialization code was also inserted in the child's atfork handler.
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D41462
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@322202 91177308-0d34-0410-b5e6-96231b3b80d8
The code is tested to work with latest clang, GNU and Intel compiler. The implementation
is optimized for low overhead when no tool is attached shifting the cost to execution with
tool attached.
This patch does not implement OMPT for libomptarget.
Patch by Simon Convent and Joachim Protze
Differential Revision: https://reviews.llvm.org/D38185
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@317085 91177308-0d34-0410-b5e6-96231b3b80d8
Removes semicolons after if {} blocks, function definitions, etc.
I was able to apply the large OMPT patch cleanly on top of this one
with no conflicts.
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@314340 91177308-0d34-0410-b5e6-96231b3b80d8
This change adds a new environment variable, KMP_TEAMS_THREAD_LIMIT, which is
used to set a new global variable, __kmp_teams_max_nth, which is checked when
determining the size and quantity of teams that will be created in the teams
construct. Specifically, it is a limit on the total number of threads in a given
teams construct. It differentiates the limits for the teams construct from the
limits for regular parallel regions (KMP_DEVICE_THREAD_LIMIT/__kmp_max_nth and
OMP_THREAD_LIMIT/__kmp_cg_max_nth). When each individual team is formed, it is
still subject to those limits. After the clauses to the teams construct are
parsed and calculated, we check to make sure we are within this limit, and if
not, reduce num_threads per team and/or number of teams, accordingly. The
default value is set to the number of available processors on the system.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D36009
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@309874 91177308-0d34-0410-b5e6-96231b3b80d8
This change fixes the implementation of OMP_THREAD_LIMIT. The implementation of
this previously was not restricted to a contention group (but it should be,
according to the spec), and this is fixed here. A field is added to root thread
to store a counter of the threads in the contention group. An extra check is
added when reserving threads for a parallel region that checks this variable and
compares to threadlimit-var, which is implemented as a new global variable,
kmp_cg_max_nth. Associated settings changes were also made, and clean up of
comments that referred to OMP_THREAD_LIMIT, but should refer to the new
KMP_DEVICE_THREAD_LIMIT (added in an earlier patch).
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D35912
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@309319 91177308-0d34-0410-b5e6-96231b3b80d8
This change drops in KMP_DEVICE_THREAD_LIMIT to replace KMP_MAX_THREADS. It's
possible there will eventually be a OMP_DEVICE_THREAD_LIMIT, and we need
something to distinguish from OMP_THREAD_LIMIT, which is currently implemented
incorrectly (the fix for that will be added soon in a separate patch).
KMP_ALL_THREADS is deprecated here, but we can keep the "all" option on
KMP_DEVICE_THREAD_LIMIT to support that functionality. KMP_DEVICE_THREAD_LIMIT
now has priority over its deprecated rival KMP_ALL_THREADS. I also cleaned up
some comments that incorrectly referred to non-existent kmp_max_threads variable
instead of kmp_max_nth.
I've left the name of where this setting eventually ends up as
__kmp_max_nth, for now.
This change does not change much in the way of functionality. It does NOT change
OMP_THREAD_LIMIT. It's just cleaning up and setting up for that.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D35860
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@309168 91177308-0d34-0410-b5e6-96231b3b80d8
Changes are: replaced C-style casts with cons_cast and reinterpret_cast;
type of several counters changed to signed; type of parameters of 32-bit and
64-bit AND and OR intrinsics changes to unsigned; changed files formatted
using clang-format version 3.8.1.
Differential Revision: https://reviews.llvm.org/D34759
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@307020 91177308-0d34-0410-b5e6-96231b3b80d8
This patch contains the clang-format and cleanup of the entire code base. Some
of clang-formats changes made the code look worse in places. A best effort was
made to resolve the bulk of these problems, but many remain. Most of the
problems were mangling line-breaks and tabbing of comments.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D32659
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@302929 91177308-0d34-0410-b5e6-96231b3b80d8
Add build option LIBOMP_OMP_VERSION=50, 5.0 headers, and add the year/month
associated with OpenMP 5.0 in relevant source locations. Also, remove the
deprecated LIBOMP_OMP_VERSION=41 option.
Patch by Olga Malysheva
Differential Revision: https://reviews.llvm.org/D30450
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@297083 91177308-0d34-0410-b5e6-96231b3b80d8
There is no corresponding free() for this expandable array. The logic is
added in __kmp_cleanup() next to the freeing of __kmp_nested_nth.
git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@292348 91177308-0d34-0410-b5e6-96231b3b80d8
Jonathan Peyton