bkietz commented on a change in pull request #8240:
URL: https://github.com/apache/arrow/pull/8240#discussion_r492829401
##########
File path: cpp/src/arrow/util/thread_pool.cc
##########
@@ -168,9 +174,11 @@ Status ThreadPool::SetCapacity(int threads) {
CollectFinishedWorkersUnlocked();
state_->desired_capacity_ = threads;
- int diff = static_cast<int>(threads - state_->workers_.size());
- if (diff > 0) {
- LaunchWorkersUnlocked(diff);
+ const int diff = threads - static_cast<int>(state_->workers_.size());
Review comment:
Maybe easier to read?
```suggestion
const int required = static_cast<int>(std::min(
threads - state_->workers_.size(),
state_->pending_tasks_.size()));
```
##########
File path: cpp/src/arrow/util/thread_pool.h
##########
@@ -182,8 +182,12 @@ class ARROW_EXPORT ThreadPool : public Executor {
int GetCapacity() override;
// Dynamically change the number of worker threads.
- // This function returns quickly, but it may take more time before the
- // thread count is fully adjusted.
+ //
+ // This function always returns immediately.
+ // If less threads are running than this number, new threads are spawned
Review comment:
```suggestion
// If fewer threads are running than this number, new threads are spawned
```
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