Resolution of Hardware Performance Counters

in this post i will try to estimate resolution and correctness of performance counters in intel processors. i should remark that these test are conducted in a single threaded application. we shouldn't forget multi-threaded programs can led very different results.

perf event open

perf is a powerful tool to measure hardware performance counters in linux. perf also provides a syscall interface to interact with various counters like llc miss.

syscall(__NR_perf_event_open, ....)

creating llc miss

creating a last level cache miss is simple. first we should create a variable, after we should flush (with using clflush instruction) from cache and access it again. trying to access this variable causes a cache miss, and cpu needs to fetch from main-memory. we can simplify this process as follow:

flush(&k);
__asm__("nop;lfence;");
access_memory(&k);

to measure correctness of performance counters we will create n number of cache misses and compare with the expected results. results are shown like that :

This was the end of the blog post. You can reach me via email umusasadik at gmail com