[Bf-blender-cvs] [e1309030603] master: BLI: avoid invoking tbb for small workloads
Jacques Lucke
noreply at git.blender.org
Thu Dec 2 12:56:58 CET 2021
Commit: e1309030603980c6b2f33486adf6ae5c2e4eb965
Author: Jacques Lucke
Date: Thu Dec 2 12:54:35 2021 +0100
Branches: master
https://developer.blender.org/rBe1309030603980c6b2f33486adf6ae5c2e4eb965
BLI: avoid invoking tbb for small workloads
We often call `parallel_for` in places with very variable
sized workloads. When many elements are processed,
using multi-threading is great, but when processing
few elements (possibly many times) using `parallel_for`
can result in significant overhead.
I measured that this improves performance by >20% in
the refactored realize instances code I'm working on
separately. The change might also help with debugging
sometimes, because the stack trace is smaller and contains
fewer irrevelant symbols.
===================================================================
M source/blender/blenlib/BLI_task.hh
===================================================================
diff --git a/source/blender/blenlib/BLI_task.hh b/source/blender/blenlib/BLI_task.hh
index da7309837c8..84d5cd39bb4 100644
--- a/source/blender/blenlib/BLI_task.hh
+++ b/source/blender/blenlib/BLI_task.hh
@@ -67,14 +67,19 @@ void parallel_for(IndexRange range, int64_t grain_size, const Function &function
return;
}
#ifdef WITH_TBB
- tbb::parallel_for(tbb::blocked_range<int64_t>(range.first(), range.one_after_last(), grain_size),
- [&](const tbb::blocked_range<int64_t> &subrange) {
- function(IndexRange(subrange.begin(), subrange.size()));
- });
+ /* Invoking tbb for small workloads has a large overhead. */
+ if (range.size() >= grain_size) {
+ tbb::parallel_for(
+ tbb::blocked_range<int64_t>(range.first(), range.one_after_last(), grain_size),
+ [&](const tbb::blocked_range<int64_t> &subrange) {
+ function(IndexRange(subrange.begin(), subrange.size()));
+ });
+ return;
+ }
#else
UNUSED_VARS(grain_size);
- function(range);
#endif
+ function(range);
}
template<typename Value, typename Function, typename Reduction>
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