Linux time sample based profiler.
- by Caspin
short version:
Is there a good time based sampling profiler for Linux?
long version:
I generally use OProfile to optimize my applications. I recently found a shortcoming that has me wondering.
The problem was a tight loop spawning c++filt to demangle a c++ name. I only stumbled upon the code by accident while chasing down another bottleneck. The OProfile didn't show anything unusual about the code so I almost ignored it but my code sense told me to optimize the call and see what happened. I changed the popen of c++filt to abi::__cxa_demangle. The runtime went from more than a minute to a little over a second. About a x60 speed up.
Is there a way I could have configured OProfile to flag the popen call? As the profile data sits now OProfile thinks the bottle neck was the heap and std::string calls (which BTW once optimized dropped the runtime to less than a second, more than x2 speed up).
Here is my OProfile configuration:
$ sudo opcontrol --status
Daemon not running
Event 0: CPU_CLK_UNHALTED:90000:0:1:1
Separate options: library
vmlinux file: none
Image filter: /path/to/excutable
Call-graph depth: 7
Buffer size: 65536
Is there another profiler for Linux that could have found the bottleneck?
I suspect the issue is that OProfile only logs its samples to the currently running process. I'd like it to always log its samples to the process I'm profiling. So if the process is currently switched out (blocking on IO or a popen call) OProfile would just place its sample at the blocked call.
If I can't fix this, OProfile will only be useful when the executable is pushing near 100% CPU. It can't help with executables that that have inefficient blocking calls.
