Reduce spurious awaken calls (#875)

When a registration is signalled from a side thread and the main thread
is blocke in `poll`, a pipe is used to interrupt the blocked `poll`
call. However, this pipe write is expensive and should only be made when
`poll` is blocked.

To avoid spurrious calls, the readiness queue tracks a `sleep_token`.
When a node is scheduled, it checks if the `sleep_token` is present. If
it is, it writes to the pipe to wake up the main thread.

Currently, the `sleep_token` isn't cleared when the blocking call to
`poll` wakes up naturally. This results in the next registration signal
to write to the pipe even though the main thread is not blocked.

This patch clears the `sleep_token` when the blocking call returns.

Fixes #785
1 file changed
tree: f1a54c6fe2871203ca5fd2ba837bfb9e89fa158f
  1. .gitignore
  2. .travis.yml
  3. CHANGELOG.md
  4. Cargo.toml
  5. LICENSE
  6. README.md
  7. appveyor.yml
  8. benches/
  9. ci/
  10. src/
  11. test/
README.md

Mio – Metal IO

Mio is a lightweight I/O library for Rust with a focus on adding as little overhead as possible over the OS abstractions.

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API documentation

This is a low level library, if you are looking for something easier to get started with, see Tokio.

Usage

To use mio, first add this to your Cargo.toml:

[dependencies]
mio = "0.6"

Then, add this to your crate root:

extern crate mio;

Features

  • Non-blocking TCP, UDP.
  • I/O event notification queue backed by epoll, kqueue, and IOCP.
  • Zero allocations at runtime
  • Platform specific extensions.

Non-goals

The following are specifically omitted from Mio and are left to the user or higher-level libraries.

  • File operations
  • Thread pools / multi-threaded event loop
  • Timers

Platforms

Currently supported platforms:

  • Linux
  • OS X
  • Windows
  • FreeBSD
  • NetBSD
  • Solaris
  • Android
  • iOS
  • Fuchsia (experimental).

There are potentially others. If you find that Mio works on another platform, submit a PR to update the list!

Libraries

Community

A group of Mio users hang out in the #mio channel on the Mozilla IRC server (irc.mozilla.org). This can be a good place to go for questions.

Contributing

Interested in getting involved? We would love to help you! For simple bug fixes, just submit a PR with the fix and we can discuss the fix directly in the PR. If the fix is more complex, start with an issue.

If you want to propose an API change, create an issue to start a discussion with the community. Also, feel free to talk with us in the IRC channel.

Finally, be kind. We support the Rust Code of Conduct.