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This is my requirement, I know that certain algorithms makes good use of Cache, some do not, some do more I/O than others on particular data set, etc. I would like to see and analyze that happening myself.
So I was wondering if there was a way I could know how a certain memory/variable is read, i.e. is it from cache, or was there a cache miss. Further if there was a page fault while retrieving this value etc.
Thanks a lot!
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To calculate a hit ratio, divide the number of cache hits with the sum of the number of cache hits, and the number of cache misses. For example, if you have 51 cache hits and three misses over a period of time, then that would mean you would divide 51 by 54. The result would be a hit ratio of 0.944.
A cache miss is an event in which a system or application makes a request to retrieve data from a cache, but that specific data is not currently in cache memory. Contrast this to a cache hit, in which the requested data is successfully retrieved from the cache.
A cache hit ratio is calculated by dividing the number of cache hits by the total number of cache hits and misses, and it measures how effective a cache is at fulfilling requests for content.
Similarly, the miss rate is the number of total cache misses divided by the total number of memory requests made to the cache. One might also calculate the number of hits or misses on reads or writes only. Clearly, a higher hit rate will generally result in higher performance.
If you really want to know when your caches are hitting/missing, modern processors have performance counters that you can use for exactly this purpose. I have used them extensively for academic research. The easiest way to use them is through perfmon2. Perfmon2 has both a library you can link into your program or a stand-alone program that will monitor an existing program. For example, here's the stand-alone program recording all level 1 data cache read requests and misses:
pfmon -eL1D_CACHE_LD:MESI,L1D_CACHE_LD:I_STATE your_program
For reference, Appendix A of this document (PDF) lists Intel's documentation on what hardware counters are available.
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I would try using the valgrind cachegrind tool, it can print out annotated source lines with the number of hits/misses in which cache for that line.
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