I have an application that I want to profile wrt how much time is spent in various activities. Since this application is I/O intensive, I want to get a report that will summarize how much time is spent in every library/system call (wall time).
I've tried oprofile, but it seems it gives time in terms of Unhalted CPU cycles (thats cputime, not real time)
I've tried strace -T, which gives wall time, but the data generated is huge and getting the summary report is difficult (and awk/py scripts exist for this ?)
Now I'm looking upto SystemTap, but I don't find any script that is close enough and can be modified, and the onsite tutorial didn't help much either. I am not sure if what I am looking for can be done.
I need someone to point me in the right direction.
Thanks a lot!
Judging from this commit, the recently released strace 4.9 supports this with:
strace -w -c
They call it "syscall latency" (and it's hard to see from the manpage alone that's what -w does).
Are you doing this just out of measurement curiosity, or because you want to find time-drains that you can fix to make it run faster?
If your goal is to make it run as fast as possible, then try random-pausing.
It doesn't measure anything, except very roughly.
It may be counter-intuitive, but what it does is pinpoint the code that will result in the greatest speed-up.
See the fntimes.stp systemtap sample script. https://sourceware.org/systemtap/examples/index.html#profiling/fntimes.stp
The fntimes.stp script monitors the execution time history of a given function family (assumed non-recursive). Each time (beyond a warmup interval) is then compared to the historical maximum. If it exceeds a certain threshold (250%), a message is printed.
# stap fntimes.stp 'kernel.function("sys_*")'
or
# stap fntimes.stp 'process("/path/to/your/binary").function("*")'
The last line of that .stp script demonstrates the way to track time consumed in a given family of functions
probe $1.return { elapsed = gettimeofday_us()-@entry(gettimeofday_us()) }
