1# A simple profiler 2Fit for lightwight usage, minimum dependency 3 4## Build 5``` 6g++ -o profiler profiler.cpp 7``` 8The code needs c++11 features, if an old g++ compiler is used, `-std=c++11` is needed. 9 10 11## How it works 12Profiler open perf-event and collect sampled (pid,callchain) pair, whether userspace call-chain is collected depends on kernel version, a new kernel which can unwind user space stack is recommended. 13For each (pid, callchain) pair, if this pid has not been symbol-collected, profiler would parse elf information based on `/proc/[pid]/maps` and `/proc/[pid]/map_files/*`; Symbols are stored in an ordered structure, C++ map, after symbols collected, each callchain address is binary searched for its function name, and then full chain is inserted into a tree. 14 15 16## Run 17The profiler would open perf event with the cgroup which controls the specified pid 18``` 19./profiler <pid> 20``` 21 22To create a perf-event cgroup 23 24cgroup v1 25``` 26mkdir /sys/fs/cgroup/perf_event/<somename> 27echo $$ > /sys/fs/cgroup/perf_event/<somename>/cgroup.procs 28# run the target progrom 29# run profiler with any pid within the cgroup 30``` 31For cgroup v2, just use /sys/fs/cgroup/<somename> 32 33 34## Example 35When profiler terminated, a report is generated, following is an example showing the performance impact from seccomp when running a high-IO program within a docker container. 36 37
