Menu
I'm writing a small program in C, and I want to measure it's performance.
I want to see how much time do it run in the processor and how many cache hit+misses has it made. Information about context switches and memory usage would be nice to have too.
The program takes less than a second to execute.
I like the information of /proc/[pid]/stat, but I don't know how to see it after the program has died/been killed.
Any ideas?
EDIT: I think Valgrind adds a lot of overhead. That's why I wanted a simple tool, like /proc/[pid]/stat, that is always there.
939
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.
What Is Cache Miss and Hit? A cache miss occurs when a cache doesn't have the requested data in its memory. Meanwhile, a hit is when a cache successfully finds the requested data, satisfying the search query. For a more effective caching system, the hit ratio should be higher than the miss rate.
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.
Use perf:
perf stat ./yourapp See the kernel wiki perf tutorial for details. This uses the hardware performance counters of your CPU, so the overhead is very small.
Example from the wiki:
perf stat -B dd if=/dev/zero of=/dev/null count=1000000 Performance counter stats for 'dd if=/dev/zero of=/dev/null count=1000000': 5,099 cache-misses # 0.005 M/sec (scaled from 66.58%) 235,384 cache-references # 0.246 M/sec (scaled from 66.56%) 9,281,660 branch-misses # 3.858 % (scaled from 33.50%) 240,609,766 branches # 251.559 M/sec (scaled from 33.66%) 1,403,561,257 instructions # 0.679 IPC (scaled from 50.23%) 2,066,201,729 cycles # 2160.227 M/sec (scaled from 66.67%) 217 page-faults # 0.000 M/sec 3 CPU-migrations # 0.000 M/sec 83 context-switches # 0.000 M/sec 956.474238 task-clock-msecs # 0.999 CPUs 0.957617512 seconds time elapsed No need to load a kernel module manually, on a modern debian system (with the linux-base package) it should just work. With the perf record -a / perf report combo you can also do full-system profiling. Any application or library that has debugging symbols will show up with details in the report.
For visualization flame graphs seem to work well. (Update 2020: the hotspot UI has flame graphs integrated.)
82
The best tool for you is called valgrind. It is capable of memory profiling, call-graph building and much more.
sudo apt get install valgrind valgrind ./yourapp However, to obtain the time your program executed, you can use time(8) linux utility.
time ./yourapp If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
