parking_lot
miri
parking_lot | miri | |
---|---|---|
7 | 122 | |
2,546 | 4,003 | |
- | 3.5% | |
7.2 | 10.0 | |
18 days ago | 5 days ago | |
Rust | Rust | |
Apache License 2.0 | Apache License 2.0 |
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parking_lot
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How fair should an unfair mutex be?
Recently I've been developing my own mutex using a lot of inspiration from the excellent parking_lot crate. The mutex in parking_lot is eventually fair in that it occasionally does a fair unlock to ensure threads aren't completely starved.
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Which Mutex to use in this case (independent tasks, partially under contention)
parking_lot still has an open issue #201: Heavily degraded performance while in extreme contention on some processors which reveals that parking_lot selfishly uses spinning locks under some circumstances to sacriice total system efficiency in the name of trying to improve its own latency. In my opinion, the only place spinning locks are excusable is fullscreen games and, even then, Linus Torvalds is of the opinion they're usually implemented wrong. (Issue 201 also includes a bunch of benchmark runs if you want to read through to figure out which one applies to the current shipping state of the codebase.)
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Why Rust mutexes look like they do
I think there was at some point the plan to make it the std implementation. However, cross platform support was kinda tricky if I remember link to an issue. I tend to suggest to always first prototype with std primitives. Often your bottlenecks are in totally different places. For example, you wait on some data C that also waits on data B but this depends on A which is a really slow query to a database.
- How to call RawRwLock.lock_exclusive() of parking_lot?
- Parking_lot: Compact and efficient synchronization primitives for Rust
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A Firehose of Rust, for busy people who know some C++
I think the current state-of-the-art in terms of high-performance, general-purpose mutexes is parking_lot. (Which was ported from a C++ project of the same name.) Rather than initializing a new underlying pthread_mutex for every instance of Mutex, it keeps a global collection of thread parking queues somewhere, which turns out to be more efficient in various ways. An individual parking_lot::Mutex doesn't require a heap allocation, and is just 1 byte in size (plus the size of T).
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Eliminating Data Races in C++ and Rust with Thread Sanitizer in Firefox – A Technical Report
The first was bug 1674770, which was a bug in the parking_lot library. This Rust library provides synchronization primitives and other concurrency tools and is written and maintained by experts. We did not investigate the impact but the issue was a couple atomic orderings being too weak and was fixed quickly by the authors. This is yet another example that proves how difficult it is to write bug-free concurrent code.
miri
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Rust: Box Is a Unique Type
>While we are many missing language features away from this being the case, the noalias case is also magic descended upon box itself, with no user code ever having access to it.
I'm not sure why the author thinks there's magic behind Box. Box is not a special case of `noalias`. Run this snippet with miri and you'll see the same issue: https://play.rust-lang.org/?version=stable&mode=debug&editio...
`Box` _does_ have an expectation that its inner pointer is not aliased to another Box (even if used for readonly operations). See: https://github.com/rust-lang/miri/issues/1800#issuecomment-8...)
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Bytecode VMs in Surprising Places
Miri [0] is an interpreter for the mid-level intermediate representation (MIR) generated by the Rust compiler. MIR is input for more processing steps of the compiler. However miri also runs MIR directly. This means miri is a VM. Of course it's not a bytecode VM, because MIR is not a bytecode AFAIK. I still think that miri is a interesting example.
And why does miri exist?
It is a lot slower. However it can check for some undefined behavior.
[0]: https://github.com/rust-lang/miri
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RFC: Rust Has Provenance
Provenance is a dynamic property of pointer values. The actual underlying rules that a program must follow, even when using raw pointers and `unsafe`, are written in terms of provenance. Miri (https://github.com/rust-lang/miri) represents provenance as an actual value stored alongside each pointer's address, so it can check for violations of these rules.
Lifetimes are a static approximation of provenance. They are erased after being validated by the borrow checker, and do not exist in Miri or have any impact on what transformations the optimizer may perform. In other words, the provenance rules allow a superset of what the borrow checker allows.
- Mir: Strongly typed IR to implement fast and lightweight interpreters and JITs
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Running rustc in a browser
There has been discussion of doing this with MIRI, which would be easier than all of rustc.
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Piecemeal dropping of struct members causes UB? (Miri)
This issue has been fixed: https://github.com/rust-lang/miri/issues/2964
- Erroneous UB Error with Miri?
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I've incidentally created one of the fastest bounded MPSC queue
Actually, I've done more advanced tests with MIRI (see https://github.com/rust-lang/miri/issues/2920 for example) which allowed me to fix some issues. I've also made the code compatible with loom, but I didn't found the time yet to write and execute loom tests. That's on the TODO-list, and I need to track it with an issue too.
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Interested in "secure programming languages", both theory and practice but mostly practice, where do I start?
He is one of the big brains behind Miri, which is a interpreter that runs on the MIR (compiler representation between human code and asm/machine code) and detects undefined behavior. Super useful tool for language safety, pretty interesting on its own.
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Formal verification for unsafe code?
I would also run your tests in Miri (https://github.com/rust-lang/miri) to try to cover more bases.
What are some alternatives?
cs_libguarded - Header-only library for multithreaded programming
cons-list - Singly-linked list implementation in Rust
sanitizers - AddressSanitizer, ThreadSanitizer, MemorySanitizer
rust - Empowering everyone to build reliable and efficient software.
Rust-Full-Stack - Rust projects here are easy to use. There are blog posts for them also.
rfcs - RFCs for changes to Rust
nomicon - The Dark Arts of Advanced and Unsafe Rust Programming
Clippy - A bunch of lints to catch common mistakes and improve your Rust code. Book: https://doc.rust-lang.org/clippy/
bacon - background rust code check
unsafe-code-guidelines - Forum for discussion about what unsafe code can and can't do
tokio - A runtime for writing reliable asynchronous applications with Rust. Provides I/O, networking, scheduling, timers, ...
mrustc - Alternative rust compiler (re-implementation)