LTTng and Erlang/OTP

20162017 Ericsson AB. All Rights Reserved. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. LTTng and Erlang/OTP 2016-04-27 LTTng.xml

Introduction

The Linux Trace Toolkit: next generation is an open source system software package for correlated tracing of the Linux kernel, user applications and libraries.

For more information, please visit http://lttng.org

Building Erlang/OTP with LTTng support

Configure and build Erlang with LTTng support:

For LTTng to work properly with Erlang/OTP you need the following packages installed:

LTTng-tools: a command line interface to control tracing sessions.

LTTng-UST: user space tracing library.

On Ubuntu this can be installed via aptitude:

$ sudo aptitude install lttng-tools liblttng-ust-dev

See Installing LTTng for more information on how to install LTTng on your system.

After LTTng is properly installed on the system Erlang/OTP can be built with LTTng support.

$ ./configure --with-dynamic-trace=lttng
$ make

Dyntrace Tracepoints

All tracepoints are in the domain of org_erlang_dyntrace

All Erlang types are the string equivalent in LTTng.

process_spawn

pid : string :: Process ID. Ex. "<0.131.0>" parent : string :: Process ID. Ex. "<0.131.0>" entry : string :: Code Location. Ex. "lists:sort/1"

Available through erlang:trace/3 with trace flag procs and {tracer,dyntrace,[]} as tracer module.

Example:

process_spawn: { cpu_id = 3 }, { pid = "<0.131.0>", parent = "<0.130.0>", entry = "erlang:apply/2" }

process_link

to : string :: Process ID or Port ID. Ex. "<0.131.0>" from : string :: Process ID or Port ID. Ex. "<0.131.0>" type : string :: "link" | "unlink"

Available through erlang:trace/3 with trace flag procs and {tracer,dyntrace,[]} as tracer module.

Example:

process_link: { cpu_id = 3 }, { from = "<0.130.0>", to = "<0.131.0>", type = "link" }

process_exit

pid : string :: Process ID. Ex. "<0.131.0>" reason : string :: Exit reason. Ex. "normal"

Available through erlang:trace/3 with trace flag procs and {tracer,dyntrace,[]} as tracer module.

Example:

process_exit: { cpu_id = 3 }, { pid = "<0.130.0>", reason = "normal" }

process_register

pid : string :: Process ID. Ex. "<0.131.0>" name : string :: Registered name. Ex. "error_logger" type : string :: "register" | "unregister"

Example:

process_register: { cpu_id = 0 }, { pid = "<0.128.0>", name = "dyntrace_lttng_SUITE" type = "register" }

process_scheduled

pid : string :: Process ID. Ex. "<0.131.0>" entry : string :: Code Location. Ex. "lists:sort/1" type : string :: "in" | "out" | "in_exiting" | "out_exiting" | "out_exited"

Available through erlang:trace/3 with trace flag running and {tracer,dyntrace,[]} as tracer module.

Example:

process_scheduled: { cpu_id = 0 }, { pid = "<0.136.0>", entry = "erlang:apply/2", type = "in" }

port_open

pid : string :: Process ID. Ex. "<0.131.0>" driver : string :: Driver name. Ex. "efile" port : string :: Port ID. Ex. "#Port<0.1031>"

Available through erlang:trace/3 with trace flag ports and {tracer,dyntrace,[]} as tracer module.

Example:

port_open: { cpu_id = 5 }, { pid = "<0.131.0>", driver = "'/bin/sh -s unix:cmd'", port = "#Port<0.1887>" }

port_exit

port : string :: Port ID. Ex. "#Port<0.1031>" reason : string :: Exit reason. Ex. "normal"

Available through erlang:trace/3 with trace flag ports and {tracer,dyntrace,[]} as tracer module.

Example:

port_exit: { cpu_id = 5 }, { port = "#Port<0.1887>", reason = "normal" }

port_link

to : string :: Process ID. Ex. "<0.131.0>" from : string :: Process ID. Ex. "<0.131.0>" type : string :: "link" | "unlink"

Available through erlang:trace/3 with trace flag ports and {tracer,dyntrace,[]} as tracer module.

Example:

port_link: { cpu_id = 5 }, { from = "#Port<0.1887>", to = "<0.131.0>", type = "unlink" }

port_scheduled

Available through erlang:trace/3 with trace flag running and {tracer,dyntrace,[]} as tracer module.

port : string :: Port ID. Ex. "#Port<0.1031>" entry : string :: Callback. Ex. "open" type : string :: "in" | "out" | "in_exiting" | "out_exiting" | "out_exited"

Example:

port_scheduled: { cpu_id = 5 }, { pid = "#Port<0.1905>", entry = "close", type = "out" }

Available through erlang:trace/3 with trace flag running and {tracer,dyntrace,[]} as tracer module.

function_call

pid : string :: Process ID. Ex. "<0.131.0>" entry : string :: Code Location. Ex. "lists:sort/1" depth : integer :: Stack depth. Ex. 0

Available through erlang:trace/3 with trace flag call and {tracer,dyntrace,[]} as tracer module.

Example:

function_call: { cpu_id = 5 }, { pid = "<0.145.0>", entry = "dyntrace_lttng_SUITE:'-t_call/1-fun-1-'/0", depth = 0 }

function_return

pid : string :: Process ID. Ex. "<0.131.0>" entry : string :: Code Location. Ex. "lists:sort/1" depth : integer :: Stack depth. Ex. 0

Available through erlang:trace/3 with trace flag call or return_to and {tracer,dyntrace,[]} as tracer module.

Example:

function_return: { cpu_id = 5 }, { pid = "<0.145.0>", entry = "dyntrace_lttng_SUITE:waiter/0", depth = 0 }

function_exception

pid : string :: Process ID. Ex. "<0.131.0>" entry : string :: Code Location. Ex. "lists:sort/1" class : string :: Error reason. Ex. "error"

Available through erlang:trace/3 with trace flag call and {tracer,dyntrace,[]} as tracer module.

Example:

function_exception: { cpu_id = 5 }, { pid = "<0.144.0>", entry = "t:call_exc/1", class = "error" }

message_send

from : string :: Process ID or Port ID. Ex. "<0.131.0>" to : string :: Process ID or Port ID. Ex. "<0.131.0>" message : string :: Message sent. Ex. "{<0.162.0>,ok}"

Available through erlang:trace/3 with trace flag send and {tracer,dyntrace,[]} as tracer module.

Example:

message_send: { cpu_id = 3 }, { from = "#Port<0.1938>", to = "<0.160.0>", message = "{#Port<0.1938>,eof}" }

message_receive

to : string :: Process ID or Port ID. Ex. "<0.131.0>" message : string :: Message received. Ex. "{<0.162.0>,ok}"

Available through erlang:trace/3 with trace flag 'receive' and {tracer,dyntrace,[]} as tracer module.

Example:

message_receive: { cpu_id = 7 }, { to = "<0.167.0>", message = "{<0.165.0>,ok}" }

gc_minor_start

pid : string :: Process ID. Ex. "<0.131.0>" need : integer :: Heap need. Ex. 2 heap : integer :: Young heap word size. Ex. 233 old_heap : integer :: Old heap word size. Ex. 233

Available through erlang:trace/3 with trace flag garbage_collection and {tracer,dyntrace,[]} as tracer module.

Example:

gc_minor_start: { cpu_id = 0 }, { pid = "<0.172.0>", need = 0, heap = 610, old_heap = 0 }

gc_minor_end

pid : string :: Process ID. Ex. "<0.131.0>" reclaimed : integer :: Heap reclaimed. Ex. 2 heap : integer :: Young heap word size. Ex. 233 old_heap : integer :: Old heap word size. Ex. 233

Available through erlang:trace/3 with trace flag garbage_collection and {tracer,dyntrace,[]} as tracer module.

Example:

gc_minor_end: { cpu_id = 0 }, { pid = "<0.172.0>", reclaimed = 120, heap = 1598, old_heap = 1598 }

gc_major_start

pid : string :: Process ID. Ex. "<0.131.0>" need : integer :: Heap need. Ex. 2 heap : integer :: Young heap word size. Ex. 233 old_heap : integer :: Old heap word size. Ex. 233

Available through erlang:trace/3 with trace flag garbage_collection and {tracer,dyntrace,[]} as tracer module.

Example:

gc_major_start: { cpu_id = 0 }, { pid = "<0.172.0>", need = 8, heap = 2586, old_heap = 1598 }

gc_major_end

pid : string :: Process ID. Ex. "<0.131.0>" reclaimed : integer :: Heap reclaimed. Ex. 2 heap : integer :: Young heap word size. Ex. 233 old_heap : integer :: Old heap word size. Ex. 233

Available through erlang:trace/3 with trace flag garbage_collection and {tracer,dyntrace,[]} as tracer module.

Example:

gc_major_end: { cpu_id = 0 }, { pid = "<0.172.0>", reclaimed = 240, heap = 4185, old_heap = 0 }

BEAM Tracepoints

All tracepoints are in the domain of org_erlang_otp

All Erlang types are the string equivalent in LTTng.

scheduler_poll

scheduler : integer :: Scheduler ID. Ex. 1 runnable : integer :: Runnable. Ex. 1

Example:

scheduler_poll: { cpu_id = 4 }, { scheduler = 1, runnable = 1 }

driver_init

driver : string :: Driver name. Ex. "efile" major : integer :: Major version. Ex. 3 minor : integer :: Minor version. Ex. 1 flags : integer :: Flags. Ex. 1

Example:

driver_init: { cpu_id = 2 }, { driver = "caller_drv", major = 3, minor = 3, flags = 1 }

driver_start

pid : string :: Process ID. Ex. "<0.131.0>" driver : string :: Driver name. Ex. "efile" port : string :: Port ID. Ex. "#Port<0.1031>"

Example:

driver_start: { cpu_id = 2 }, { pid = "<0.198.0>", driver = "caller_drv", port = "#Port<0.3676>" }

driver_output

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile" bytes : integer :: Size of data returned. Ex. 82

Example:

driver_output: { cpu_id = 2 }, { pid = "<0.198.0>", port = "#Port<0.3677>", driver = "/bin/sh -s unix:cmd", bytes = 36 }

driver_outputv

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile" bytes : integer :: Size of data returned. Ex. 82

Example:

driver_outputv: { cpu_id = 5 }, { pid = "<0.194.0>", port = "#Port<0.3663>", driver = "tcp_inet", bytes = 3 }

driver_ready_input

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

Example:

driver_ready_input: { cpu_id = 5 }, { pid = "<0.189.0>", port = "#Port<0.3637>", driver = "inet_gethost 4 " }

driver_ready_output

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

Example:

driver_ready_output: { cpu_id = 5 }, { pid = "<0.194.0>", port = "#Port<0.3663>", driver = "tcp_inet" }

driver_timeout

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

Example:

driver_timeout: { cpu_id = 5 }, { pid = "<0.196.0>", port = "#Port<0.3664>", driver = "tcp_inet" }

driver_stop_select

driver : string :: Driver name. Ex. "efile"

Example:

driver_stop_select: { cpu_id = 5 }, { driver = "unknown" }

driver_flush

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

Example:

driver_flush: { cpu_id = 7 }, { pid = "<0.204.0>", port = "#Port<0.3686>", driver = "tcp_inet" }

driver_stop

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

Example:

driver_stop: { cpu_id = 5 }, { pid = "[]", port = "#Port<0.3673>", driver = "efile" }

driver_process_exit

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

driver_ready_async

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile"

Example:

driver_ready_async: { cpu_id = 3 }, { pid = "<0.181.0>", port = "#Port<0.3622>", driver = "efile" }

driver_call

pid : string :: Process ID. Ex. "<0.131.0>" port : string :: Port ID. Ex. "#Port<0.1031>" driver : string :: Driver name. Ex. "efile" command : integer :: Command integer. Ex. 1 bytes : integer :: Size of data returned. Ex. 82

Example:

driver_call: { cpu_id = 2 }, { pid = "<0.202.0>", port = "#Port<0.3676>", driver = "caller_drv", command = 0, bytes = 2 }

driver_control

Example:

driver_control: { cpu_id = 3 }, { pid = "<0.32767.8191>", port = "#Port<0.0>", driver = "forker", command = 83, bytes = 32 }

aio_pool_get

port : string :: Port ID. Ex. "#Port<0.1031>" length : integer :: Async queue length. Ex. 0

Example:

aio_pool_get: { cpu_id = 4 }, { port = "#Port<0.3614>", length = 0 }

aio_pool_put

port : string :: Port ID. Ex. "#Port<0.1031>" length : integer :: Async queue length. Ex. -1

Async queue length is not defined for put operations.

Example:

aio_pool_put: { cpu_id = 3 }, { port = "#Port<0.3614>", length = -1 }

carrier_create

type : string :: Carrier type. Ex. "ets_alloc" instance : integer :: Allocator instance. Ex. 1 size : integer :: Carrier size. Ex. 262144 mbc_carriers : integer :: Number of multiblock carriers in instance. Ex. 3 mbc_carriers_size : integer :: Total size of multiblock blocks carriers in instance. Ex. 1343488 mbc_blocks : integer :: Number of multiblock blocks in instance. Ex. 122 mbc_blocks_size : integer :: Total size of all multiblock blocks in instance. Ex. 285296 sbc_carriers : integer :: Number of singleblock carriers in instance. Ex. 1 sbc_carriers_size : integer :: Total size of singleblock blocks carriers in instance. Ex. 1343488 sbc_blocks : integer :: Number of singleblocks in instance. Ex. 1 sbc_blocks_size : integer :: Total size of all singleblock blocks in instance. Ex. 285296

Example:

carrier_create: { cpu_id = 2 }, { type = "ets_alloc", instance = 7, size = 2097152, mbc_carriers = 4, mbc_carriers_size = 3440640, mbc_blocks = 526, mbc_blocks_size = 1278576, sbc_carriers = 0, sbc_carriers_size = 0, sbc_blocks = 0, sbc_blocks_size = 0 }

carrier_destroy

Example:

carrier_destroy: { cpu_id = 6 }, { type = "ets_alloc", instance = 7, size = 262144, mbc_carriers = 3, mbc_carriers_size = 3178496, mbc_blocks = 925, mbc_blocks_size = 2305336, sbc_carriers = 0, sbc_carriers_size = 0, sbc_blocks = 0, sbc_blocks_size = 0 }

carrier_pool_put

type : string :: Carrier type. Ex. "ets_alloc" instance : integer :: Allocator instance. Ex. 1 size : integer :: Carrier size. Ex. 262144

Example:

carrier_pool_put: { cpu_id = 3 }, { type = "ets_alloc", instance = 5, size = 1048576 }

carrier_pool_get

type : string :: Carrier type. Ex. "ets_alloc" instance : integer :: Allocator instance. Ex. 1 size : integer :: Carrier size. Ex. 262144

Example:

carrier_pool_get: { cpu_id = 7 }, { type = "ets_alloc", instance = 4, size = 3208 }

Example of process tracing

An example of process tracing of os_mon and friends.

Clean start of lttng in a bash shell.

$ lttng create erlang-demo
Spawning a session daemon
Session erlang-demo created.
Traces will be written in /home/egil/lttng-traces/erlang-demo-20160526-165920

Start an Erlang node with lttng enabled.

$ erl
Erlang/OTP 19 [erts-8.0] [source-4d7b24d] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false] [lttng]

Eshell V8.0  (abort with ^G)
1>

Load the dyntrace module.

1> l(dyntrace).
{module,dyntrace}

All tracepoints via dyntrace are now visibile and can be listed through lttng list -u.

Enable the process_register LTTng tracepoint for Erlang.

$ lttng enable-event -u org_erlang_dyntrace:process_register
UST event org_erlang_dyntrace:process_register created in channel channel0

Enable process tracing for new processes and use dyntrace as tracer backend.

2> erlang:trace(new,true,[procs,{tracer,dyntrace,[]}]).
0

Start LTTng tracing.

$ lttng start
Tracing started for session erlang-demo

Start the os_mon application in Erlang.

3> application:ensure_all_started(os_mon).
{ok,[sasl,os_mon]}

Stop LTTng tracing and view the result.

$ lttng stop
Tracing stopped for session erlang-demo
$ lttng view
[17:20:42.561168759] (+?.?????????) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.66.0>", name = "sasl_sup", type = "register" }
[17:20:42.561215519] (+0.000046760) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.67.0>", name = "sasl_safe_sup", type = "register" }
[17:20:42.562149024] (+0.000933505) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.68.0>", name = "alarm_handler", type = "register" }
[17:20:42.571035803] (+0.008886779) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.69.0>", name = "release_handler", type = "register" }
[17:20:42.574939868] (+0.003904065) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.74.0>", name = "os_mon_sup", type = "register" }
[17:20:42.576818712] (+0.001878844) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.75.0>", name = "disksup", type = "register" }
[17:20:42.580032013] (+0.003213301) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.76.0>", name = "memsup", type = "register" }
[17:20:42.583046339] (+0.003014326) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.78.0>", name = "cpu_sup", type = "register" }
[17:20:42.586206242] (+0.003159903) elxd1168lx9 org_erlang_dyntrace:process_register: \
    { cpu_id = 5 }, { pid = "<0.82.0>", name = "timer_server", type = "register" }