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  1. Erlang/OTP
  2. ERL-355

LTTng dynamic tracing: 'depth' field for 'function_call' for 'function_return' tracepoints

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    Details

    • Type: New Feature
    • Status: Help Wanted
    • Priority: Minor
    • Resolution: Unresolved
    • Affects Version/s: 19.1.1
    • Fix Version/s: None
    • Component/s: runtime_tools
    • Labels:
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      Description

      When using 'function_call' and 'function_return' tracepoints, LTTng viewer always show 'depth = 0' regardless of the actual stack depth. Following is the sample of the LTTng viewer output showing one function calling another, with the inner function call and return having 'depth = 0' (whereas it should have been 1):

      [20:56:09.773366183] (+0.000000084) jabber-node03 org_erlang_dyntrace:function_call:

      { cpu_id = 4 }, { pid = "<0.31599.6>", entry = "ezlib:process/2", depth = 0 }
      [20:56:09.773379981] (+0.000000136) jabber-node03 org_erlang_dyntrace:function_call: { cpu_id = 4 }

      ,

      { pid = "<0.31599.6>", entry = "ezlib_nif:process_buffer/2", depth = 0 }

      [20:56:09.773399320] (+0.000000762) jabber-node03 org_erlang_dyntrace:function_return:

      { cpu_id = 4 }, { pid = "<0.31599.6>", entry = "ezlib_nif:process_buffer/2", depth = 0 }
      [20:56:09.773406352] (+0.000000256) jabber-node03 org_erlang_dyntrace:function_return: { cpu_id = 4 }

      ,

      { pid = "<0.31599.6>", entry = "ezlib:process/2", depth = 0 }

      Having depth value right is critical for us to properly analyze the traces, as it gives a shield against lost lttng records and/or function calls that do not return (either by design or for other reasons).

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            Assignee:
            otp_team_vm Team VM
            Reporter:
            boris.okner Boris Okner
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              Dates

              Created:
              Updated: