Metrics Modes

The two metrics modes are where a trace file is read in and processed by one or more cache configurations. They are designed to generate runtime metrics enabling comparison of cache performance based on the cahce's configuration and the sequence of memory accesses (trace file) produced by different benchmarks.

CohereSim counts the occurrence of many different events and prints them to stdout after the last trace is processed. The output is in CSV format, allowing the user to directly import the data into their choice of spreadsheet software (or save it for later) by redirecting stdout to a .csv file. The output contains one column for each of the statistics defined in the bus_msg_e and statistic_e enums, in addition to a miss rate column which is computed using other statistics. Since CohereSim processes multicore memory accesses for one or more configurations, config and core columns are included as identifyers in the output.

CohereSim does not process input from stdin in these two modes.

Single

In this mode, a single cache configuration is specified on the command line. Consequently, the value of the config field in the output is always 0, which indicates the command line as the source.

The command line arguments are <cache_size[unit]> <line_size> <associativity> <coherence> <replacer> <directory> <trace_file> [trace_limit]

associativity: The number of ways in the cache. In other words, the number of cache lines in a set.
cache_size: The size of the cache in bytes. Optionally, 'k' or 'M' can be specified as the unit. For instance, one can specify '128k' instead of '131072'.
coherence: The name of the coherence protocol the cache should implement (not case sensitive)
directory: The name of the cirectory protocol the cache should implement (not case sensitive)
line_size: The size of a single cache line in bytes.
replacer: The name of the replacement policy the cache should implement (not case sensitive)
trace_file: The trace file that CohereSim should read in
trace_limit: (Optional) The maximum number of traces CohereSim should process

Note:: Every cache dimension must be a power of 2. Any other value is rejected by CohereSim.

Batch

This mode of operation is designed to accelerate the production of the runtime metrics by reading a trace file once, but processing it across multiple cache configurations in parallel. As such, the value of the config field in the output indicates which line of the configs file was the source for the configuration that the accompanying statistics are for. The cache configurations are specified in a configs file, where each line is one instance of the first 6 command line arguments for 'Single Metric' mode, cache_size[unit], line_size, associativity, coherence, replacer, and directory.

Note:: Due to each configuration processing the trace file in parallel, the order of configurations in the output is arbitrary. A single configuration's output, however, is guaranteed to be contiguous.

The command line arguments for this mode are <configs_file> <trace_file> [trace_limit]

configs_file: The file containing a series of cache configurations
trace_file: The trace file that CohereSim should read in
trace_limit: (Optional) The maximum number of traces CohereSim should process

Interactive Mode

Interactive mode is designed not to produce metrics, but instead to allow the user to interactively investigate the behavior of any protocol or policy that a cache may implement.

CohereSim processes input received on stdin and prints the resulting state and any actions to stdout formatted as a table. The table generally reads left-to-right, top-to-bottom, and contains a series of command-action-result entries. CohereSim continues processing input until EOF, which will never occur if the input is from the terminal. In this case, sending the program interupt signal (Ctrl+C or Ctrl+D) will close stdin instead of terminating the program, thus causing the program to exit naturally.

The single command line argument is the name of the policy/protocol to showcase (not case sensitive). Depending on the choice, interactive mode will respond to a different set of commands (all case insensitive), detailed below:

Coherence Protocol:

E<n>: Evict cache line n
R<n>: Read access on cache line n
W<n>: Write access on cache line n
X: Reset all internal state and start a new table

Replacement Policy:

<tag>: Access line with a tag of tag. Only letters A-Z are allowed as the tag
-: Reset all internal state and start a new table

Table of Contents

Metrics Modes

Single

Batch

Interactive Mode