Design a new prefetcher for fetching data from main memory to cache hierarchy.

[szuhzw]

Hello. Which files do I need to modify in the Hermes project if I want to design a new prefetcher for fetching data from main memory to cache hierarchy? Thank you. @rahulbera

[rahulbera]

There are two ways to do this:

• Option 1: (a) Define your own prefetcher in a separate file. E.g., if it's a L2 prefetcher, define it as myprefetcher.l2c_pref, if it's an LLC prefetcher, call it myprefetcher.llc_pref. (b) Build ChampSim with this prefetcher of choice (i.e., pass the prefetcher name in the build_champsim.sh script). See ChampSim documentation to know more.
• Option 2: Define the internal logic of your prefetcher as we have done in scooby.cc. See the prefetcher/streamer.cc file for an easiest example. All you have to do is to (a) create a class for your prefetcher as a dervied class of Prefetcher (see inc/streamer.h for example), (b) define three key functions for this new prefetcher's operation: invoke_prefetcher, print_config, and dump_stats, (c) call this prefetcher from the multi prefetcher interface: in case for L2/LLC prefetcher, call it from multi.l2c_pref or multi.llc_pref, respectively.

The first option binds the prefetcher at compile time. So if you have to try and test different prefetchers, you have to compile different versions of ChampSim with appropriate prefetchers. The second option binds a prefetcher at runtime: you just need to compile once and select which prefetcher to use at runtime using l2c_prefetcher_types or llc_prefetcher_types knobs. But the option 2, due to it's runtime bind, may run a bit slower than option 1.