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authorTom Tromey <tom@tromey.com>2021-05-23 09:04:27 -0600
committerTom Tromey <tom@tromey.com>2022-04-12 09:31:16 -0600
commit82d734f7a3b6f08813a9ad6272aa026779c88975 (patch)
tree26aea3dcb439f9c8a884535c60eb452ffcebc423 /gdbsupport
parentc0892a1d5dc29eb849e9aed0fb7c7dade6dffb23 (diff)
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Add batching parameter to parallel_for_each
parallel_for_each currently requires each thread to process at least 10 elements. However, when indexing, it's fine for a thread to handle just a single CU. This patch parameterizes this, and updates the one user.
Diffstat (limited to 'gdbsupport')
-rw-r--r--gdbsupport/parallel-for.h18
1 files changed, 12 insertions, 6 deletions
diff --git a/gdbsupport/parallel-for.h b/gdbsupport/parallel-for.h
index 915814e..811ffd6 100644
--- a/gdbsupport/parallel-for.h
+++ b/gdbsupport/parallel-for.h
@@ -32,11 +32,16 @@ namespace gdb
This approach was chosen over having the callback work on single
items because it makes it simple for the caller to do
- once-per-subrange initialization and destruction. */
+ once-per-subrange initialization and destruction.
+
+ The parameter N says how batching ought to be done -- there will be
+ at least N elements processed per thread. Setting N to 0 is not
+ allowed. */
template<class RandomIt, class RangeFunction>
void
-parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
+parallel_for_each (unsigned n, RandomIt first, RandomIt last,
+ RangeFunction callback)
{
/* So we can use a local array below. */
const size_t local_max = 16;
@@ -48,10 +53,11 @@ parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
size_t n_elements = last - first;
if (n_threads > 1)
{
- /* Arbitrarily require that there should be at least 10 elements
- in a thread. */
- if (n_elements / n_threads < 10)
- n_threads = std::max (n_elements / 10, (size_t) 1);
+ /* Require that there should be at least N elements in a
+ thread. */
+ gdb_assert (n > 0);
+ if (n_elements / n_threads < n)
+ n_threads = std::max (n_elements / n, (size_t) 1);
size_t elts_per_thread = n_elements / n_threads;
n_actual_threads = n_threads - 1;
for (int i = 0; i < n_actual_threads; ++i)