In -depth study of the DISK LRU Cache algorithm and implementation
In -depth study of the DISK LRU Cache algorithm and implementation
introduction:
In modern computer systems, cache is one of the key parts of improvement of system performance.In order to cope with the tedious I/O operation, cache can temporarily store data or data in the network in order to quickly access and read.Among them, the LRU (recently used) algorithm is a classic cache replacement strategy. It is based on data -based access history records to choose which older cache items are replaced.The DISK LRU Cache algorithm is a special implementation of the LRU algorithm in the disk cache. It provides an efficient disk cache solution by effectively replacing the cache items with low heat.
1. Introduction to algorithms
1. Overview of LRU algorithm
The core idea of the LRU algorithm is: when the cache space is full, the recent cache items used at least used to free up the space to store new cache items.The advantage of this is that the commonly used data can be retained in the cache and reducing the expenses of I/O access.
2. DISK LRU CACHE algorithm
The DISK LRU Cache algorithm is an extension of the LRU algorithm, which is used for disk cache scenes.Unlike the memory cache, the access of disk cache is much slower, so it needs to be more intelligent cache management strategies.The DISK LRU Cache algorithm stores the data to the file in the disk, and uses a two -way linked list to record the access history of the cache item in order to select the appropriate cache item for replacement.
2. Algorithm implementation
Here are a simple implementation example based on the Java class library:
import java.io.File;
import java.util.LinkedHashMap;
import java.util.Map;
public class DiskLruCache {
private final LinkedHashMap<String, String> cache;
private final int maxSize;
private int currentSize;
public DiskLruCache(int maxSize) {
this.maxSize = maxSize;
this.cache = new LinkedHashMap<String, String>(0, 0.75f, true) {
@Override
protected boolean removeEldestEntry(Map.Entry<String, String> eldest) {
return currentSize > maxSize;
}
};
this.currentSize = 0;
}
public void put(String key, String value) {
File file = new File(key);
currentSize += value.getBytes().length;
cache.put(key, value);
}
public String get(String key) {
return cache.get(key);
}
}
The above example shows the implementation of a simple disk Lru Cache.In the constructing function, we pass the cache maximum Maxsize.The access order of the cache item is recorded by linkedhashmap. Among them, the overwriting of the RemovelDestentry method allows the cache item to automatically remove at least the cache item when the current cache size exceeds MaxSize.The PUT method is used to add a new cache item to the cache, and the get method is used to obtain the corresponding cache value according to the key.
in conclusion:
The Disk Lru Cache algorithm is an efficient disk cache management strategy. It provides a way to effectively manage disk cache through the idea and implementation of the LRU algorithm.In actual development, we can reasonably manage the cache based on business needs and system performance optimization needs, combined with the Disk Lru Cache algorithm to improve the response speed and performance of the system.
