2019-01-15 17:17:55 +03:00
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# snmalloc
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2020-02-28 12:03:41 +03:00
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snmalloc is a high-performance allocator.
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snmalloc can be used directly in a project as a header-only C++ library,
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it can be `LD_PRELOAD`ed on Elf platforms (e.g. Linux, BSD),
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and there is a [crate](https://crates.io/crates/snmalloc-rs) to use it from Rust.
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Its key design features are:
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2019-01-15 17:17:55 +03:00
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* Memory that is freed by the same thread that allocated it does not require any
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synchronising operations.
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* Freeing memory in a different thread to initially allocated it, does not take
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any locks and instead uses a novel message passing scheme to return the
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2020-02-28 12:03:41 +03:00
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memory to the original allocator, where it is recycled. This enables 1000s of remote
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deallocations to be performed with only a single atomic operation enabling great
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scaling with core count.
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2019-01-15 17:17:55 +03:00
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* The allocator uses large ranges of pages to reduce the amount of meta-data
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required.
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2020-02-28 12:03:41 +03:00
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* The fast paths are highly optimised with just two branches on the fast path
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for malloc (On Linux compiled with Clang).
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* The platform dependencies are abstracted away to enable porting to other platforms.
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snmalloc's design is particular well suited to the following two difficult
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scenarios that can be problematic for other allocators:
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* Allocations on one thread are freed by a different thread
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* Deallocations occur in large batches
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Both of these can cause massive reductions in performance of other allocators, but
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do not for snmalloc.
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2019-01-15 17:17:55 +03:00
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2020-02-28 12:03:41 +03:00
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Comprehensive details about snmalloc's design can be found in the
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[accompanying paper](snmalloc.pdf), and differences between the paper and the
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2019-05-23 20:49:19 +03:00
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current implementation are [described here](difference.md).
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2020-02-28 12:03:41 +03:00
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Since writing the paper, the performance of snmalloc has improved considerably.
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2019-05-23 17:13:47 +03:00
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2019-01-16 20:19:22 +03:00
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[](https://dev.azure.com/snmalloc/snmalloc/_build/latest?definitionId=1?branchName=master)
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2020-11-10 16:33:45 +03:00
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# Further documentation
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2020-06-30 15:33:50 +03:00
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2020-11-10 16:33:45 +03:00
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- [Instructions for building snmalloc](docs/BUILDING.md)
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- [Instructions for porting snmalloc](docs/PORTING.md)
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2020-06-30 15:33:50 +03:00
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2019-01-09 17:05:58 +03:00
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# Contributing
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This project welcomes contributions and suggestions. Most contributions require you to agree to a
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Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us
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the rights to use your contribution. For details, visit https://cla.microsoft.com.
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When you submit a pull request, a CLA-bot will automatically determine whether you need to provide
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a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions
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provided by the bot. You will only need to do this once across all repos using our CLA.
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This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/).
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For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or
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contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.
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