2 releases
0.0.1 | Aug 12, 2024 |
---|---|
0.0.0 | Aug 10, 2024 |
#28 in #malloc
37 downloads per month
79KB
2K
SLoC
Emma is an EMbeddable Memory Allocator. This means:
- Fully
no_std
compatible. - No direct or indirect binary dependencies, including on
libc
: emma uses raw syscalls instead. Note that your rustc target may depend onlibc
- use thex86_64-unknown-linux-unknown
target, with which emma is compatible, if you want to avoid this. - No usage of any shared resources: Instead of
brk
/sbrk
to modify the shared data segment, emma only ever maps its own segments usingmmap
.
Multiple emma instances can coexist with other allocators the same process. If its symbols are renamed, emma can even coexist with other copies and/or versions of itself without interference!
Usage
Use emma as you would any other allocator:
#[global_allocator]
static EMMA: emma::DefaultEmma = emma::DefaultEmma::new();
Performance
Emma seems not far behind (other) state-of-the-art allocators.
Target Architecture
At the moment, emma exclusively targets linux on x86_64
.
Known Issues
- It is not clear how emma behaves when a process is forked. (Note: child processes of multi-threaded processes may only access async-signal-safe functions until they call
execve
anyway.) - Calling
fork
(or performing an equivalentclone
call) is safe as long as no thread is currently de-/allocating memory. However, if the forking process ever allocated memory on more than one thread, memory usage will be suboptimal until the new main thread terminates. - Embedding multiple emma instancess into one process should work, but unless their symbols are renamed they may share data structures behind the scenes.
- An emma instance does not return all its resources, even if all allocations are returned. This is reasonable for a global allocator, but makes it not as useful as a temporary allocator.
- Emma is not async-signal-safe, i.e., you may not de-/allocate memory in a signal handler. (The same probably holds true for your default memory allocator; POSIX does not list
malloc
orfree
as async-signal safe either.)
Features
tls
enabling thread-local-storage requires a nightly compiler. Enablingtls
massively increases performance.boundary-checks
enables assertions at the library boundary. These assertions cost a small amount of performance.
License
Licensed under either of:
- Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
Contributions
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
Dependencies
~12MB
~301K SLoC