Merge pull request #73 from jonhoo/left-right

This patch set sxtract the core concurrency primitive from evmap by implementing the plan from #45 (comment). It fixes #45 and #70 by allowing separate implementations of the data structure that re-use the concurrency primitive. Fixes #67 by making `ReadGuard::map` public.
jonhoo · Nov 29, 2020 · 81d84ee · 81d84ee
2 parents d4c12b8 + b334b2c
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diff --git a/Cargo.toml b/Cargo.toml
@@ -1,36 +1,2 @@
-[package]
-name = "evmap"
-version = "11.0.0-alpha.1"
-authors = ["Jon Gjengset <[email protected]>"]
-edition = "2018"
-license = "MIT OR Apache-2.0"
-
-readme = "README.md"
-description = "A lock-free, eventually consistent, concurrent multi-value map."
-repository = "https://github.com/jonhoo/rust-evmap.git"
-
-keywords = ["map","multi-value","lock-free"]
-categories = ["concurrency", "data-structures"]
-
-[badges]
-azure-devops = { project = "jonhoo/jonhoo", pipeline = "evmap", build = "8" }
-codecov = { repository = "jonhoo/rust-evmap", branch = "master", service = "github" }
-maintenance = { status = "passively-maintained" }
-
-[features]
-default = []
-indexed = ["indexmap"]
-eviction = ["indexed", "rand"]
-
-[dependencies]
-indexmap = { version = "1.1.0", optional = true }
-smallvec = "1.0.0"
-hashbag = "0.1.2"
-bytes = { version = "0.5", optional = true }
-rand = { version = "0.7", default-features = false, features = ["alloc"], optional = true }
-slab = "0.4"
-
-[dev-dependencies]
-quickcheck = "0.9"
-quickcheck_macros = "0.9"
-rand = "0.7"
+[workspace]
+members = ["evmap", "evmap-derive", "left-right"]
diff --git a/README.md b/README.md
@@ -1,41 +1,30 @@
-# evmap
+This crate holds the implementation of the `left-right` concurrency
+primitive, and its primary user `evmap`. See the documentation for each
+crate for details.
+
+Left-right is a concurrency primitive for high concurrency reads over a
+single-writer data structure. The primitive keeps two copies of the
+backing data structure, one that is accessed by readers, and one that is
+access by the (single) writer. This enables all reads to proceed in
+parallel with minimal coordination, and shifts the coordination overhead
+to the writer. In the absence of writes, reads scale linearly with the
+number of cores.
+
+[![Crates.io](https://img.shields.io/crates/v/left-right.svg)](https://crates.io/crates/left-right)
+[![Documentation](https://docs.rs/left-right/badge.svg)](https://docs.rs/left-right/)
 
 [![Crates.io](https://img.shields.io/crates/v/evmap.svg)](https://crates.io/crates/evmap)
 [![Documentation](https://docs.rs/evmap/badge.svg)](https://docs.rs/evmap/)
+
 [![Build Status](https://dev.azure.com/jonhoo/jonhoo/_apis/build/status/evmap?branchName=master)](https://dev.azure.com/jonhoo/jonhoo/_build/latest?definitionId=8&branchName=master)
 [![Codecov](https://codecov.io/github/jonhoo/rust-evmap/coverage.svg?branch=master)](https://codecov.io/gh/jonhoo/rust-evmap)
 
-A lock-free, eventually consistent, concurrent multi-value map.
-
-This map implementation allows reads and writes to execute entirely in parallel, with no
-implicit synchronization overhead. Reads never take locks on their critical path, and neither
-do writes assuming there is a single writer (multi-writer is possible using a `Mutex`), which
-significantly improves performance under contention.
-
-The trade-off exposed by this module is one of eventual consistency: writes are not visible to
-readers except following explicit synchronization. Specifically, readers only see the
-operations that preceeded the last call to `WriteHandle::refresh` by a writer. This lets
-writers decide how stale they are willing to let reads get. They can refresh the map after
-every write to emulate a regular concurrent `HashMap`, or they can refresh only occasionally to
-reduce the synchronization overhead at the cost of stale reads.
-
-For read-heavy workloads, the scheme used by this module is particularly useful. Writers can
-afford to refresh after every write, which provides up-to-date reads, and readers remain fast
-as they do not need to ever take locks.
-
-The map is multi-value, meaning that every key maps to a *collection* of values. This
-introduces some memory cost by adding a layer of indirection through a `Vec` for each value,
-but enables more advanced use. This choice was made as it would not be possible to emulate such
-functionality on top of the semantics of this map (think about it -- what would the operational
-log contain?).
-
-To faciliate more advanced use-cases, each of the two maps also carry some customizeable
-meta-information. The writers may update this at will, and when a refresh happens, the current
-meta will also be made visible to readers. This could be useful, for example, to indicate what
-time the refresh happened.
-
 ## Performance
 
+**These benchmarks are outdated at this point, but communicate the right
+point. Hopefully I'll have a chance to update them again some time
+soon.**
+
 I've run some benchmarks of evmap against a standard Rust `HashMap` protected
 by a [reader-writer
 lock](https://doc.rust-lang.org/std/sync/struct.RwLock.html), as well as

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
@@ -1,75 +1,93 @@
-jobs:
- - template: default.yml@templates
-   parameters:
-     minrust: 1.40.0
-     codecov_token: $(CODECOV_TOKEN_SECRET)
- - job: derive
-   displayName: "Test evmap-derive"
-   pool:
-     vmImage: ubuntu-latest
-   steps:
-     - template: install-rust.yml@templates
-     - script: cargo test
-       displayName: cargo test
- - job: benchmark
-   displayName: "Check that benchmark compiles"
-   pool:
-     vmImage: ubuntu-latest
-   steps:
-     - template: install-rust.yml@templates
-     - bash: cd benchmark && cargo check
-       displayName: cargo check benchmark/
- - job: miri
-   displayName: "Run miri on test suite"
-   pool:
-     vmImage: ubuntu-latest
-   steps:
-     - bash: |
-         echo '##vso[task.setvariable variable=nightly]nightly-'$(curl -s https://rust-lang.github.io/rustup-components-history/x86_64-unknown-linux-gnu/miri)
-       displayName: "Determine latest miri nightly"
-     - template: install-rust.yml@templates
-       parameters:
-         rust: $(nightly)
-         components:
-           - miri
-     - script: cargo miri setup
-       displayName: cargo miri setup
-     - script: cargo miri test
-       displayName: cargo miri test
-       env:
-         QUICKCHECK_TESTS: 500
- - job: asan
-   displayName: "Run address sanitizer on test suite"
-   pool:
-     vmImage: ubuntu-latest
-   steps:
-     - template: install-rust.yml@templates
-       parameters:
-         rust: nightly
-     - bash: |
-           sudo ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer
-       displayName: Enable debug symbols
-     # only --lib --tests b/c of https://github.com/rust-lang/rust/issues/53945
-     - script: |
-           env ASAN_OPTIONS="detect_odr_violation=0" RUSTFLAGS="-Z sanitizer=address" cargo test --lib --tests --target x86_64-unknown-linux-gnu
-       displayName: cargo -Z sanitizer=address test
- - job: lsan
-   displayName: "Run leak sanitizer on test suite"
-   pool:
-     vmImage: ubuntu-latest
-   steps:
-     - template: install-rust.yml@templates
-       parameters:
-         rust: nightly
-     - bash: |
-           sudo ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer
-           sed -i '/\[features\]/i [profile.dev]' Cargo.toml
-           sed -i '/profile.dev/a opt-level = 1' Cargo.toml
-           cat Cargo.toml
-       displayName: Enable debug symbols
-     - script: |
-           env RUSTFLAGS="-Z sanitizer=leak" cargo test --target x86_64-unknown-linux-gnu
-       displayName: cargo -Z sanitizer=leak test
+stages:
+ - stage: left_right
+   jobs:
+    - template: default.yml@templates
+      parameters:
+        minrust: 1.40.0
+        dir: "left-right"
+ - stage: evmap
+   jobs:
+    - template: default.yml@templates
+      parameters:
+        minrust: 1.40.0
+        codecov_token: $(CODECOV_TOKEN_SECRET)
+        dir: "evmap"
+    - job: derive
+      displayName: "Test evmap-derive"
+      pool:
+        vmImage: ubuntu-latest
+      steps:
+        - template: install-rust.yml@templates
+          parameters:
+            components:
+              - rust-src
+        - script: cargo test
+          displayName: cargo test
+          workingDirectory: "evmap-derive"
+    - job: benchmark
+      displayName: "Check that benchmark compiles"
+      pool:
+        vmImage: ubuntu-latest
+      steps:
+        - template: install-rust.yml@templates
+        - script: cargo check
+          displayName: cargo check benchmark/
+          workingDirectory: "evmap/benchmark"
+    - job: miri
+      displayName: "Run miri on test suite"
+      pool:
+        vmImage: ubuntu-latest
+      steps:
+        - bash: |
+            echo '##vso[task.setvariable variable=nightly]nightly-'$(curl -s https://rust-lang.github.io/rustup-components-history/x86_64-unknown-linux-gnu/miri)
+          displayName: "Determine latest miri nightly"
+        - template: install-rust.yml@templates
+          parameters:
+            rust: $(nightly)
+            components:
+              - miri
+        - script: cargo miri setup
+          displayName: cargo miri setup
+          workingDirectory: "evmap"
+        - script: cargo miri test
+          displayName: cargo miri test
+          workingDirectory: "evmap"
+          env:
+            QUICKCHECK_TESTS: 500
+    - job: asan
+      displayName: "Run address sanitizer on test suite"
+      pool:
+        vmImage: ubuntu-latest
+      steps:
+        - template: install-rust.yml@templates
+          parameters:
+            rust: nightly
+        - bash: |
+              sudo ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer
+          displayName: Enable debug symbols
+        # only --lib --tests b/c of https://github.com/rust-lang/rust/issues/53945
+        - script: |
+              env ASAN_OPTIONS="detect_odr_violation=0" RUSTFLAGS="-Z sanitizer=address" cargo test --lib --tests --target x86_64-unknown-linux-gnu
+          displayName: cargo -Z sanitizer=address test
+          workingDirectory: "evmap"
+    - job: lsan
+      displayName: "Run leak sanitizer on test suite"
+      pool:
+        vmImage: ubuntu-latest
+      steps:
+        - template: install-rust.yml@templates
+          parameters:
+            rust: nightly
+        - bash: |
+              sudo ln -s /usr/bin/llvm-symbolizer-6.0 /usr/bin/llvm-symbolizer
+              sed -i '/\[features\]/i [profile.dev]' Cargo.toml
+              sed -i '/profile.dev/a opt-level = 1' Cargo.toml
+              cat Cargo.toml
+          displayName: Enable debug symbols
+        - script: |
+              env RUSTFLAGS="-Z sanitizer=leak" cargo test --target x86_64-unknown-linux-gnu
+          displayName: cargo -Z sanitizer=leak test
+          workingDirectory: "evmap"
 
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