Feature #20855
open
Introduce `Fiber::Scheduler#blocking_region` to avoid stalling the event loop.
Description
The current Fiber Scheduler performance can be significantly impacted by blocking operations that cannot be deferred to the event loop, particularly in high-concurrency environments where Fibers rely on non-blocking operations for efficient task execution.
Problem Description¶
Fibers in Ruby are designed to improve performance and responsiveness by allowing concurrent tasks to proceed without blocking one another. However, certain operations inherently block the fiber scheduler, leading to delayed execution across other fibers. When blocking operations are inevitable, such as system or CPU bound operations without event-loop support, they create bottlenecks that degrade the scheduler's overall performance.
Proposed Solution¶
The proposed solution in PR https://github.com/ruby/ruby/pull/11963 introduces a blocking_region hook in the fiber scheduler to improve handling of blocking operations. This addition allows code that releases the GVL (Global VM Lock) to be lifted out of the event loop, reducing the performance impact on the scheduler during blocking calls. By isolating these operations from the primary event loop, this enhancement aims to improve worst case performance in the presence of blocking operations.
blocking_region(work)¶
The new, optional, fiber scheduler hook blocking_region accepts an opaque callable object work, which encapsulates work that can be offloaded to a thread pool for execution. If the hook is not implemented rb_nogvl executes as usual.
Example¶
require "zlib"
require "async"
require "benchmark"
DATA = Random.new.bytes(1024*1024*100)
duration = Benchmark.measure do
Async do
10.times do
Async do
Zlib.deflate(DATA)
end
end
end
end
# Ruby 3.3.4: ~16 seconds
# Ruby 3.4.0 + PR: ~2 seconds.
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