Dtrace没有为NodeJS收集任何数据

Question

I'm trying to profile NodeJS with Dtrace and it is not working out. The command that I'm using is:

dtrace -n 'profile-97/execname == "node" && arg1/{@[jstack(150, 8000)] = count(); } tick-60s { exit(0); }' > stacks.out

The output that I get is:

CPU     ID                    FUNCTION:NAME
  0 312432                        :tick-30s

If I do dtrace -l then I get for example:

58814      instr            kernel              setup_APIC_eilvt-jne 0xffffffff81045e27
58815      instr            kernel               setup_APIC_eilvt-je 0xffffffff81045e34
58816      instr            kernel               setup_APIC_eilvt-je 0xffffffff81045e38
58817      instr            kernel            setup_APIC_eilvt-callr 0xffffffff81045e46
58818      instr            kernel            setup_APIC_eilvt-callr 0xffffffff81045e6a
58819      instr            kernel      lapic_timer_setup.part.4-cli 0xffffffff81045ea0
58820      instr            kernel      lapic_timer_setup.part.4-jbe 0xffffffff81045eaa
58821      instr            kernel      lapic_timer_setup.part.4-jbe 0xffffffff81045eaf
58822      instr            kernel    lapic_timer_setup.part.4-callr 0xffffffff81045ed4
58823      instr            kernel              lapic_timer_setup-je 0xffffffff81045f39
58824      instr            kernel            lapic_timer_setup-repz 0xffffffff81045f3b
58825      instr            kernel     local_apic_timer_interrupt-je 0xffffffff81045f74
58826      instr            kernel  local_apic_timer_interrupt-callr 0xffffffff81045f90
58827      instr            kernel     local_apic_timer_interrupt-je 0xffffffff81045f99
58828      instr            kernel              clear_local_APIC-jne 0xffffffff8104610e
58829      instr            kernel               clear_local_APIC-jg 0xffffffff810461c3
58830      instr            kernel               clear_local_APIC-je 0xffffffff8104629a
58831      instr            kernel            disable_local_APIC-jne 0xffffffff810463bd
58832      instr            kernel             disable_local_APIC-je 0xffffffff810463c7
58833      instr            kernel          disable_local_APIC-callr 0xffffffff810463c9
58834      instr            kernel           disable_local_APIC-repz 0xffffffff81046400
58835      instr            kernel                 lapic_suspend-jne 0xffffffff8104641d
58836      instr            kernel                  lapic_suspend-jg 0xffffffff81046555
58837      instr            kernel                 lapic_suspend-cli 0xffffffff81046561
58838      instr            kernel               lapic_suspend-callr 0xffffffff81046568

And if I list all the processes that open files with:

dtrace -q -n syscall::open:entry'{ printf("%-16s%-16s\n", execname,copyinstr(arg0)); }'

I get all the processes opening files, it even show NodeJS starting and getting ready for work :)

vminfo          /var/run/utmp
vminfo          /var/run/utmp
systemd         /proc/145/cgroup
vminfo          /var/run/utmp
vminfo          /var/run/utmp
vminfo          /var/run/utmp
vminfo          /var/run/utmp
systemd         /proc/460/cgroup
vminfo          /var/run/utmp
vminfo          /var/run/utmp
node            /etc/ld.so.cache
node            /lib/x86_64-linux-gnu/libdl.so.2
node            /lib/x86_64-linux-gnu/librt.so.1
node            /usr/lib/x86_64-linux-gnu/libstdc++.so.6
node            /lib/x86_64-linux-gnu/libm.so.6
node            /lib/x86_64-linux-gnu/libgcc_s.so.1
node            /lib/x86_64-linux-gnu/libpthread.so.0
node            /lib/x86_64-linux-gnu/libc.so.6
node            /dev/urandom
node            /home/davidgatti/test/ble.js
node            /etc/resolv.conf
node            /etc/nsswitch.conf
node            /dev/urandom
node            /dev/pts/0
node            /dev/null
node            /dev/pts/0
vminfo          /var/run/utmp
vminfo          /var/run/utmp
systemd         /proc/145/cgroup

Question

What I'm doing wrong? How should I probe NodeJS or any other process to get some useful info out?

Answer 1

Sadly this won't work under Linux because Dtrace it strictly tied with the system kernel.

Dtrace works for example under macOS or Solaris because there is one version of the kernel, and if any changes are made the authors can do the appropriate changed to Dtrace.

Since not only Linux has many different kernels in each distribution, you are free to compile your own version however you want, and this means that it is impossible to create a working Dtrace for this system.

Since Dtrace needs to hook in specific parts of the kernel to be able to trace what is going on within the app.

You can read more about this in the Issue section of the original Dtrace for linux repo.