I've been meaning to. I took a quick look now: # rr record date rr: Saving the execution of `date' to trace directory `/root/.local/share/rr/date-30'. [F

I've been meaning to. I took a quick look now: # rr record date rr: Saving the execution of `date' to trace directory `/root/.local/share/rr/date-30'. [FATAL /build/rr-jR8ti5/rr-4.1.0/src/PerfCounters.cc:195:start_counter() errno: 2 'No such file or directory'] -> Unable to open performance counter with 'perf_event_open'; are perf events enabled? Try 'perf record'. Aborted oh-oh... # gdb `which rr` [...] (gdb) r record date Starting program: /usr/bin/rr record date [...] [FATAL /build/rr-jR8ti5/rr-4.1.0/src/PerfCounters.cc:195:start_counter() errno: 2 'No such file or directory'] -> Unable to open performance counter with 'perf_event_open'; are perf events enabled? Try 'perf record'. Thread 1 "rr" received signal SIGABRT, Aborted. 0x00007ffff6d6b418 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54 54 ../sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) bt #0 0x00007ffff6d6b418 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54 #1 0x00007ffff6d6d01a in __GI_abort () at abort.c:89 #2 0x00000000005a9133 in FatalOstream::~FatalOstream() () #3 0x00000000006303fc in ?? () #4 0x0000000000630679 in PerfCounters::reset(long) () #5 0x00000000006cbd8f in Task::resume_execution(ResumeRequest, WaitRequest, TicksRequest, int) () #6 0x0000000000638be9 in RecordSession::task_continue(Task*, RecordSession::StepState const&) () #7 0x000000000063d70e in RecordSession::record_step() () #8 0x00000000006354b6 in ?? () #9 0x00000000006356f2 in RecordCommand::run(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&) () #10 0x000000000061f44d in main () I did a bit more gdb debugging (one debugger debugging another, although it's a bit hard as rr is stripped and doesn't have a debuginfo package!), and it looks like it's trying to use PMCs. No PMCs here: EC2 Xen guest. So rr won't work, for me or EC2's 1+ million other customers. Perhaps rr can switch to software events?