Cache associativiy studies

The target of the study is to receive miss rates on different cache configurations using a real memory request trace as a input workload. Changing the cache size and associativity (number of ways) you will obtain a chart like the following one:

Note that the form of your curves can be different from ones on the picture, as you have another workload.

Remember that our goal is to investigate the most effective cache configuration for the given program (it can be done if the miss rates, size and power of each configuration are known). It can be surprised, but to do that we do not need to execute the program. We even do not need to know what instructions the program contains and what they do. The only thing we have to know is a sequence of addresses of memory accesses generated by the program.

To measure the miss rate you have to go through this sequence, check each address (using CacheTagArray::read method) and calculate the number of hits and misses. It is important that when CacheTagArray::read finds out a miss the address has to be written into the tags array (using CacheTagArray::write method). It needs to be done, because in the real cache a missed block is downloaded from the main memory (or the next cache) and then is written into the cache. Of course, after a hit there should not be any write into the cache (and, consequently, into the cache array). After a hit you just move to the next address in the sequence.

Configurations

It this study you investigate only the different combinations of cache size (size_in_bytes) and associativity (ways). All of them are specified in the following table:

You should gather the miss rate for each cell of this table for each workload (i.e. address sequence).

The other parameters of the cache are always the same in this study: block_size_in_bytes = 4, addr_size_in_bits = 32. But your model still have to support their changing if it is needed.

Note: when a simulation starts the cache is considered to be empty (for each new configuration and workload).

Input data

Your program (located in miss_rate_sim.cpp) should take as the first parameter the name of a text file where addresses of cache requests are located. The example of such file you can found at <trunk>/mem_trace.txt. The beginning of the file is presented below:

0x11018 0x11060 0x11030 0x11050 0x5220d0 0x11040 0x11090 0x5221a0 0x522220

Note: that addresses are presented in hexadecimal format, i.e 0x465b118 instead of 73773336 and separated by a space.

Output data

Output data should be presented in the CSV format where numbers in a row are miss rates for a certain cache size and they are separated by commas. Each row corresponds to the certain associativity.

In fact, it will be the table from the Configurations chapter above.

An example of the output is presented below:

0.349048, 0.27356, 0.216863, 0.164309, 0.127481, 0.0896536, 0.0614431, 0.0385261, 0.0342199, 0.0278209, 0.0277584, 
0.341117, 0.254755, 0.194426, 0.154902, 0.119156, 0.085989, 0.0524071, 0.0354602, 0.0275645, 0.0275323, 0.0271651, 
0.337479, 0.255616, 0.190327, 0.149961, 0.118951, 0.0860855, 0.0507263, 0.0303543, 0.0275824, 0.0271651, 0.0271651, 
0.338298, 0.256382, 0.192536, 0.149813, 0.118232, 0.0861409, 0.0500471, 0.0283276, 0.0271651, 0.0271651, 0.0271651, 
0.338556, 0.25701, 0.193569, 0.150662, 0.118576, 0.0856468, 0.0495244, 0.027711, 0.0271651, 0.0271651, 0.0271651, 
0.340405, 0.258033, 0.194169, 0.151537, 0.119232, 0.0850615, 0.0501856, 0.0271651, 0.0271651, 0.0271651, 0.0271651,

The first row contains miss rates for 1 way set-associative cache. It starts from the size of 1 KB and ends with 1 MB. The second row contains data for 2 ways set-associate cache and so on.

Note: that data for each associativity starts from a new line creating a new row.

Command line arguments

Your program (located in miss_rate_sim.cpp) should receive two argument from the command line. The first one is the name of an input file with memory access addresses. The second is the name of an output file where miss rates are printed in the CSV format.

For example, if an input file is located in the same folder as the executive file the command line can be the following:

miss_rate_sim.exe mem_trace.txt miss_rate.csv

Note: if there are not enough arguments or the names are incorrect your program has to cancel and to display a proper message about a reason of the failure.