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Plugin V2 Example - LRU Cache with Hooks

This example demonstrates how to create a plugin for libCacheSim using the v2 hook-based plugin system. The plugin implements a standalone LRU (Least Recently Used) cache algorithm that integrates with libCacheSim's plugin_cache.c framework.

Files

  • plugin_lru.cpp - The main LRU cache plugin implementation using hooks
  • test_hooks_plugin.c - Comprehensive test program for the plugin
  • CMakeLists.txt - Build configuration for creating the shared library

Building

To compile the plugin into a shared library:

# Prerequisites: Install Ninja build system if not already available
# Ubuntu/Debian: sudo apt install ninja-build
# macOS: brew install ninja

mkdir build
cd build
cmake -G Ninja ..
ninja

This will create:

  • libplugin_lru_hooks.so - Shared library
  • test_hooks_plugin - Test executable for validation

Plugin Architecture

The plugin implements a standalone LRU cache using C++ with a C interface for compatibility with libCacheSim. It uses:

  • StandaloneLRU Class: C++ implementation with doubly-linked list and hash map
  • Hook Functions: C interface functions that plugin_cache.c calls

Hook Functions

The plugin implements these required hook functions:

  • cache_init_hook() - Initialize the LRU cache data structure
  • cache_hit_hook() - Handle cache hits (move object to head of LRU list)
  • cache_miss_hook() - Handle cache misses (insert new object)
  • cache_eviction_hook() - Evict least recently used object and return its ID
  • cache_remove_hook() - Remove specific object from cache
  • cache_free_hook() - Clean up and free the LRU cache data structure

Usage

With cachesim Binary

# Run cachesim with the plugin
./bin/cachesim ../data/cloudPhysicsIO.vscsi vscsi lru,pluginCache 0.01,0.1 \
  -e "plugin_path=/path/to/libCacheSim/example/plugin_v2/build/libplugin_lru_hooks.so"

Testing the Plugin

Run the included test to verify plugin functionality:

cd build
./test_hooks_plugin

The test compares the plugin LRU implementation against libCacheSim's built-in LRU to ensure identical behavior.

Dependencies

  • libCacheSim: Headers and libraries from the main project
  • CMake 3.12+: Build system

Plugin Parameter Format

When using the plugin with cachesim or other libCacheSim tools, use the format:

plugin_path=/full/path/to/libplugin_lru_hooks.so

Implementation Notes

  • The plugin uses C++ internally but exports C functions for compatibility
  • Memory management is handled automatically by the StandaloneLRU destructor
  • The implementation maintains the same LRU semantics as libCacheSim's built-in LRU
  • Thread safety is not implemented - suitable for single-threaded use cases

Troubleshooting

  • Ensure the plugin path uses the plugin_path= prefix format
  • Verify all dependencies are available (check with ldd libplugin_lru_hooks.so)
  • Use absolute paths when specifying the plugin location