[ruby-core:119772] [Ruby master Feature#20876] Introduce `Fiber::Scheduler#blocking_operation_wait` to avoid stalling the event loop.
From:
"ioquatix (Samuel Williams) via ruby-core" <ruby-core@...>
Date:
2024-11-06 12:28:18 UTC
List:
ruby-core #119772
Issue #20876 has been reported by ioquatix (Samuel Williams).
----------------------------------------
Feature #20876: Introduce `Fiber::Scheduler#blocking_operation_wait` to avoid stalling the event loop.
https://bugs.ruby-lang.org/issues/20876
* Author: ioquatix (Samuel Williams)
* Status: Open
----------------------------------------
This is an evolution of the previous proposal: https://bugs.ruby-lang.org/issues/20855
## Background
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.
## Proposal
Pull Request: https://github.com/ruby/ruby/pull/12016
We will introduce a new fiber scheduler hook called `blocking_operation_work`:
```ruby
class MySchduler
# ...
def blocking_operation_wait(work)
# Example implementation:
Thread.new(&work).join
end
end
```
We introduce a new flag for `rb_nogvl`: `RB_NOGVL_BLOCKING_OPERATION` which indicates that `rb_nogvl(func, ...)` is a blocking operation that is safe to execute on a different thread or thread pool.
When a C extension invokes `rb_nogvl(..., RB_NOGVL_BLOCKING_OPERATION)`, and a fiber scheduler is available, all the arguments will be saved into a instance of a callable object (at this time a `Proc`) called `work`. When `work` is `#call`ed, it will execute `rb_nogvl` again with all the same arguments.
The fiber scheduler can decide how to execute that work, e.g. on a separate thread, to mitigate the performance impact of the blocking operation on the event loop.
## Example
Using the branch of `async` gem: https://github.com/socketry/async/pull/352/files and enabling zlib deflate to use this feature, the following performance improvement was achieved:
```ruby
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.
```
---Files--------------------------------
clipboard-202411070126-fbqpn.png (135 KB)
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