Adding Support: Configurable Cache Replacement Policies

[govardhnn]

This discussion is to validate my suggestions in configuring the cache-replacement policies, and making it easy to add more replacement policies to Olympia. Building on Issue#61.

Problem Statement:

Currently, Olympia's CacheFuncModel is hardcoded to TreePLRU from Sparta. The SimpleCache2 model from Sparta uses the ReplacementIF Interface, and also consists of implementations of LRU and MRU implemented in the same LRUReplacement.hpp

Proposed Solution:

1. I have added parameters to L1-D, L1-I and L2 Cache to select the cache replacement algorithm in their header files. To preserve backward compatibility, I have set the default configuration to TreePLRU.

2. Modified CacheFuncModel which takes the defined replacement configuration and associativity, Created a new ReplacementFactory(in Olympia) where we can configure the required policy.

I would like to make new policies local to Olympia: Random replacement, and FIFO and LIFO as sugggested by @h0lyalg0rithm, in his documentation for the LSU. I am guessing that MRU and LRU can be borrowed from Sparta as-is.

Doubt

Since for any new replacement policy I add need to use ReplacementIF for SimpleCache2, I am currently stuck at wondering how to modify the new ReplacementFactory to make my local policies use the Sparcian ReplacementIF. Any suggestions/directions from the experts would be highly appreciated!

My current code (work in progress) can be viewed at PR#230.

[govardhnn]

The following parameters added can be checked as follows:

$ ./olympia --show-parameters --no-run | grep replacement 
| | | | +-replacement_policy : [<top.cpu.core0.icache.params.replacement_policy tags:[SPARTA_Parameter]>]<param std::string replacement_policy=TreePLRU, def=TreePLRU, write=0 read: 0 ignored: 0> (privacy: 0)
| | | | +-replacement_policy : [<top.cpu.core0.dcache.params.replacement_policy tags:[SPARTA_Parameter]>]<param std::string replacement_policy=TreePLRU, def=TreePLRU, write=0 read: 0 ignored: 0> (privacy: 0)
| | | | +-replacement_policy : [<top.cpu.core0.l2cache.params.replacement_policy tags:[SPARTA_Parameter]>]<param std::string replacement_policy=TreePLRU, def=TreePLRU, write=0 read: 0 ignored: 0> (privacy: 0)