Corundum: A Persistent Memory Programming Library in Rust

crndm provides persistent memory support for Rust applications. This is useful for developing safe persistent memory applications without concerning much about crash consistency and data loss.

Carefully using Rust's strict type checking rules and borrowing mechanism, crndm guarantees that the implementation is free of common persistent memory related bugs. crndm leaves the software implementation with zero persistent memory related problems of the following types:

• A persistent pointer pointing to the volatile heap,
• Cross pool pointers,
• Unrecoverable modification to data,
• Data inconsistency due to power-failure,
• plus All memory-related issues that Rust handles.

Developers will see these issues during the design time. Therefore, it lowers the risk of making mistakes. crndm's programming model consists of using safe persistent pointers and software transactional memory.

Three pointer-wrappers lie at the heart of crndm interface. Developers may use them to allocate persistent memory safely.

• Pbox<T>: the simplest form of dynamic allocation,
• Prc<T>: a single-thread reference counted pointer for shared persistent objects,
• Parc<T>: a thread-safe reference-counted pointer for shared persistent objects.

Dependencies

crndm depends on some unstable features of Rust. Therefore, it requires nightly Rust compiler 1.50.0-nightly. Please run the following commands to download the latest version of Rust (See [https://www.rust-lang.org/tools/install] for more details).

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
rustup default nightly

Corundum is also partially dependent on a few 3rd party crates which are listed in Cargo.toml.

Usage

Use either of the following instructions to add crndm in your Cargo.toml dependencies section:

[dependencies]
crndm = { git = "https://github.com/NVSL/Corundum.git" }

Or (will be available in crates.io, soon)

[dependencies]
crndm = "0.1.0"

Memory Pools

A memory pool is a type that implements all necessary interfaces for working with persistent memory. You can use the default memory pool, or define a new memory pool type. The latter requires your type implementing MemPool trait. Please see the pass-through allocator as an example. To automatically implement a new pool type, pool!() macro is provided which creates a new module with a BuddyAlloc type.

crndm::pool!(my_pool);

Opening a memory pool file

The first thing to do is to open the memory pool file(s) before using it. You can do this by using either open() or open_no_root() methods. The first one returns a the root object given a root object type. The second one returns a guard object; the pool remains open as long as the root/guard object is in the scope. The open functions take a pool file path and a flag set to create the pool file.

if let Ok(_) = my_mod::BuddyAlloc::open_no_root("image", O_F) {
    println!("Image file is formatted and ready to use");
} else {
    println!("No image file found");
}

if let Ok(root) = my_mod::BuddyAlloc::open::<Root>("image", O_F) {
    println!("Image file is formatted and the root object is created ({:?})", root);
} else {
    println!("No image file");
}

PM Safe Data Structures

You may define any data structure with the given pointers, and without any raw pointers or references. Corundum helps you to write the right code down the road.

use crndm::rc::Prc;
use crndm::cell::LogCell;

type A = BuddyAlloc;

struct MyData {
    id: i32,
    link: Option<Prc<LogRefCell<MyData, A>, A>>
}

You may find it disturbing to specify the pool in every type. Corundum uses type aliasing and procedural macros to provide an easier way for defining new data structures. The pool!() macro aliases all persistent types associated with the internal pool type. For example

pool!(my_pool);
use my_pool::*;

struct MyData {
    id: i32,
    link: Option<Prc<PRefCell<MyData>>>
}

PClone and Root procedural macros can also be used to automatically derive the implementation of the corresponding traits for the type.

use crndm::default::*;

#[derive(PClone, Root)]
struct MyData {
    id: i32,
    link: Option<Prc<PRefCell<MyData>>>
}

Transactional Memory

crndm does not allow any modification to the protected data outside a transaction. To let mutably borrowing the protected data, you may wrap it in LogCell, Mutex, etc., and use their corresponding interface for interior mutability which requires a reference to a journal object. To obtain a journal, you may use transaction.

transaction(|j| {
    let my_data = Prc::new(LogRefCell::new(
        MyData {
            id: 1,
            link: None
        }), j);
    let mut my_data = my_data.borrow_mut(j);
    my_data.id = 2;
})

Documentation

Please visit the Documentation page for more information.

Issues and Contribution

Please feel free to report any bug using GitHub issues.

If you have other questions or suggestions, you can contact us at cse-nvsl-discuss@eng.ucsd.edu.

License

'crndm' crate is licensed under Apache License, Version 2.0, (http://www.apache.org/licenses/LICENSE-2.0).

Unless You explicitly state otherwise, any Contribution intentionally submitted for inclusion in the Work by You to the Licensor shall be under the terms and conditions of this License, without any additional terms or conditions.