How to use perf with ld_preload?

Question

I tried to use perf stat with LD_PRELOAD as prefix for executable such as:

perf stat LD_PRELOAD=$PWD/../user/preload.so ./write 1

It seems not work for perf, are there any way to achieve it?

Answer 1

perf stat env LD_PRELOAD=....  ./write 1

That should work, although that means /usr/bin/env is the process being profiled so you're getting its overhead, too. At least it's cheaper than a command like sh -c 'LD_PRELOAD=... exec ./write 1'.

If startup overhead becomes a problem, you can have your write itself fork/exec perf stat -p <PID> on itself. perf stat for part of program