systemtap profiling gc node.js


I installed node.js(0.9.4) via nvm, which according to changelog has systemtap support.

I installed systemtap on my Fedora linux distro.

$ sudo yum install systemtap

I used this gist from Ben Noordhuis.

$ stap -l 'process("node")'

produces nothing.

$ sudo stap gc.stp -c 'node test.js'
semantic error: while resolving probe point: identifier 'process' at gc.stp:7:7
        source: probe process("node").mark("gc__start")

semantic error: no match
semantic error: while resolving probe point: identifier 'process' at :12:7
        source: probe process("node").mark("gc__done")

I have no experience at all with systemtap, but like to toy with it? What is possible with it? Can I see how much memory is consumed by code(

Update to answer comment.

$ readelf -n node

readelf: Error: 'node': No such file

$ which node

$ readelf -n ~/nvm/v0.9.4/bin/node

Notes at offset 0x0000021c with length 0x00000020:
  Owner                 Data size   Description
  GNU                  0x00000010   NT_GNU_ABI_TAG (ABI version tag)
    OS: Linux, ABI: 2.6.32

Notes at offset 0x0000023c with length 0x00000024:
  Owner                 Data size   Description
  GNU                  0x00000014   NT_GNU_BUILD_ID (unique build ID bitstring)
    Build ID: 294da933883eaeaf7e848073dc3db6bff6762fb4

$ uname -a
[alfred@alfred81-AMILO-Pi-2515 gc-stap]$ uname -a
Linux alfred81-AMILO-Pi-2515.lan 3.6.3-1.fc17.x86_64 #1 SMP Mon Oct 22 15:32:35 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

$ stap -V
Systemtap translator/driver (version 2.0/0.154, rpm 2.0-1.fc17)
Copyright (C) 2005-2012 Red Hat, Inc. and others
This is free software; see the source for copying conditions.
Problem courtesy of: Alfred


Your copy of node appears to be compiled without sys/sdt.h markers. If they were compiled in, readelf -n would show something like ...

  stapsdt              0x00000040   NT_STAPSDT (SystemTap probe descriptors)
    Provider: stap
    Name: stap_system__spawn
    Location: 0x000000000012e1b0, Base: 0x00000000001cb886, Semaphore: 0x0000000000000000
    Arguments: -4@%ebx -4@%eax

Perhaps it was configured with --without-dtrace.

Solution courtesy of: fche


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