🍒 5.5 [Concurrency] Limit queue width with set_width SPI call on linux #39742
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@swift-ci please test |
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@swift-ci please nominate |
DougGregor
approved these changes
Oct 14, 2021
This was referenced Oct 15, 2021
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Description: To avoid thread explosions, i.e. thread growth to the hardcoded number of 255 when tasks are blocked on Linux, and in order to get the same behavior as Swift Concurrency has on Darwin (and back deployment), we must set the global queue width as we set it up for swift concurrency. Without this, when tasks block for even short burtsts, we end up with many many threads on Linux systems. The fix sets the width, same as we do on back deployment and gets us consistent behavior across platforms, and no thread explosions.
Risk: Low, this is how it was supposed to work to begin with.
Review by: @DougGregor
Testing: Verified the fix works manually on Ubuntu boxes, with sample applications. A bit hard to test this automatically, as we'd need to check for thread counts in the system.
Original PR: #39732
Radar: rdar://79907041