1 LTTng and Erlang/OTP
1.1 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
1.2 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
1.3 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. "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. "tcp_inet"
- 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 }
1.4 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. "tcp_inet"
- 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. "tcp_inet"
- 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. "tcp_inet"
- 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. "tcp_inet"
- 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. "tcp_inet"
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. "tcp_inet"
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. "tcp_inet"
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. "tcp_inet"
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. "tcp_inet"
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. "tcp_inet"
Example:
driver_stop: { cpu_id = 5 }, { pid = "[]", port = "#Port<0.3673>", driver = "tcp_inet" }
driver_process_exit
- pid : string :: Process ID. Ex. "<0.131.0>"
- port : string :: Port ID. Ex. "#Port<0.1031>"
- driver : string :: Driver name. Ex. "tcp_inet"
driver_ready_async
- pid : string :: Process ID. Ex. "<0.131.0>"
- port : string :: Port ID. Ex. "#Port<0.1031>"
- driver : string :: Driver name. Ex. "tcp_inet"
Example:
driver_ready_async: { cpu_id = 3 }, { pid = "<0.181.0>", port = "#Port<0.3622>", driver = "tcp_inet" }
driver_call
- pid : string :: Process ID. Ex. "<0.131.0>"
- port : string :: Port ID. Ex. "#Port<0.1031>"
- driver : string :: Driver name. Ex. "tcp_inet"
- 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
- pid : string :: Process ID. Ex. "<0.131.0>"
- port : string :: Port ID. Ex. "#Port<0.1031>"
- driver : string :: Driver name. Ex. "tcp_inet"
- command : integer :: Command integer. Ex. 1
- bytes : integer :: Size of data returned. Ex. 82
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
- 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_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 }
1.5 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" }