Restructured dynamic loop dispatcher code.
Fixed use of dispatch buffers for nonmonotonic dynamic (static_steal) schedule:
- eliminated possibility of stealing iterations of the wrong loop when victim
thread changed its buffer to work on another loop;
- fixed race when victim thread changed its buffer to work in nested parallel;
- eliminated "static" property of the schedule, that is now a single thread can
execute whole loop.
Differential Revision: https://reviews.llvm.org/D103648
Following tests were disabled for clang-11 after upgrading to
version 5.0 in D82963:
1. openmp/runtime/test/env/kmp_set_dispatch_buf.c
2. openmp/runtime/test/worksharing/for/kmp_set_dispatch_buf.c
They are also failing for clang-12. Thus this temporary disabling
until they are fixed.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D84241
Following tests are failing after upgrading to version 5.0 but are passing
for version 4.5:
1. openmp/runtime/test/env/kmp_set_dispatch_buf.c
2. openmp/runtime/test/worksharing/for/kmp_set_dispatch_buf.c
To be enabled as soon as these tests are fixed.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D82963
The problem is the lack of dispatch buffers when thousands of loops with nowait,
about 10 iterations each, are executed by hundreds of threads. We only have
built-in 7 dispatch buffers, but there is a need in dozens or hundreds of
buffers.
The problem can be fixed by setting KMP_MAX_DISP_BUF to bigger value. In order
to give users same possibility I changed build-time control into run-time one,
adding API just in case.
This change adds an environment variable KMP_DISP_NUM_BUFFERS and a new API
function kmp_set_disp_num_buffers(int num_buffers).
The KMP_DISP_NUM_BUFFERS envirable works only before serial initialization,
because during the serial initialization we already allocate buffers for the hot
team, so it is too late to change the number of buffers later (or we need to
reallocate buffers for all teams which sounds too complicated). The
kmp_set_defaults() routine does not work for this envirable, because it calls
serial initialization before reading the parameter string. So a new routine,
kmp_set_disp_num_buffers(), is created so that it can set our internal global
variable before the library initialization. If both the envirable and API used
the envirable wins.
Differential Revision: http://reviews.llvm.org/D20697
llvm-svn: 271318
AndreyChurbanov