Adaptive replacement cache

1. A method for caching a block, comprising:

receiving a request to store the block in a cache, wherein the cache is structured to comprise a most recently used (MRU) portion and a most frequently used (MFU) portion, wherein the MRU portion comprises a first evictable list and a first non-evictable list, and the MFU portion comprises a second evictable list and a second non-evictable list, wherein the first and second evictable lists are linked lists that store blocks that have no active references and the first and second non-evictable lists are linked lists that store blocks that have at least one active reference;

determining whether the cache is able to expand;

if the cache is able to expand:

expanding the cache at runtime to obtain an expanded cache, wherein expanding the cache comprises increasing the size of the cache, and

storing the block in the expanded cache;

if the cache is not able to expand:

determining whether evictable blocks are present in the cache;

if evictable blocks are present in the cache:

determining whether a total size of the evictable blocks is greater than or equal to a size of the block;

evicting a sufficient number of the evictable blocks from the cache and storing the block in the cache, if the total size of the evictable blocks is greater than or equal to the size of the block; and

activating a cache throttle, if the total size of the evictable blocks is less than the size of the block.

2. The method of claim 1 , wherein blocks in each of the linked lists are organized from newest to oldest.

3. The method of claim 1 , wherein the cache supports multiple block sizes.

4. The method of claim 1 , wherein determining whether to expand the cache comprises determining whether a memory state of a system in which the cache resides is low.

5. The method of claim 1 , wherein evicting the sufficient number of the evictable blocks from the cache comprises:

evicting evictable blocks in the MRU portion of the cache; and

evicting evictable blocks in the MFU portion of the cache only if the sufficient number of evictable blocks is not present in the MRU.

6. A system, comprising:

a cache structured to comprise a most recently used (MRU) portion and a most frequently used (MFU) portion, wherein the MRU portion comprises a first evictable list and a first non-evictable list, and the MFU portion comprises a second evictable list and a second non-evictable list, wherein the first and second evictable lists are linked lists that store blocks that have no active references and the first and second non-evictable lists are linked lists that store blocks that have at least one active reference,

wherein the cache is configured to:

receive a request to store a block;

determine whether the cache is able to expand;

if the cache is able to expand:

expand the cache at runtime to obtain an expanded cache, wherein expanding the cache comprises increasing the size of the cache, and

store the block in the expanded cache;

if the cache is not able to expand:

determine whether evictable blocks are present in the cache;

if evictable blocks are present in the cache:

determine whether a total size of the evictable blocks is greater than or equal to a size of the block;

evict a sufficient number of the evictable blocks from the cache and store the block in the cache, if the total size of the evictable blocks is greater than or equal to the size of the block; and

activate a cache throttle, if the total size of the evictable blocks is less than the size of the block.

7. The system of claim 6 , wherein the blocks in each of the linked lists are organized from newest to oldest.

8. The system of claim 6 , wherein a size of the block is within a range of 512 bytes and 128 K.

9. The system of claim 6 , wherein determining whether to expand the cache comprises determining whether a memory state of a system in which the cache resides is low.