Reduce _idle_semaphore calls in ThreadPoolExecutor

[jackcvr]

Feature or enhancement

In concurrent.futures.thread.ThredPoolExecutor method executor._idle_semaphore.release() should be called if only work queue is empty

Pitch

Currently _idle_semaphore.release() is called after processing every item in queue. That produces useless semaphore updates in case when queue still has items to process.
The optimization is going to increase processing speed of work queue.

Linked PRs

• gh-102024: Reduced _idle_semaphore.release calls #102025
• [3.12] gh-102024: Reduced _idle_semaphore.release calls (GH-102025) #104959

[terryjreedy]

'IDLE' (capitalized) is the IDE that comes with CPython; it has nothing to do with inactivity ;-).

[gpshead]

thanks!