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The implementation is still hidden behind ERTS_ENABLE_LOCK_COUNT, and
all categories are still enabled by default, but the actual counting can be
toggled at will.
OTP-13170
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Magic references are *intentionally* indistinguishable from ordinary
references for the Erlang software. Magic references do not change
the language, and are intended as a pure runtime internal optimization.
An ordinary reference is typically used as a key in some table. A
magic reference has a direct pointer to a reference counted magic
binary. This makes it possible to implement various things without
having to do lookups in a table, but instead access the data directly.
Besides very fast lookups this can also improve scalability by
removing a potentially contended table. A couple of examples of
planned future usage of magic references are ETS table identifiers,
and BIF timer identifiers.
Besides future optimizations using magic references it should also
be possible to replace the exposed magic binary cludge with magic
references. That is, magic binaries that are exposed as empty
binaries to the Erlang software.
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- Termination of a process...
- Modify trace flags of process...
- Process info on process...
- Register/unregister of name on process...
- Set group leader on process...
... while it is executing a dirty NIF.
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All 'EXIT' and monitor messages are sent from 'system'
Timeouts are "sent" from 'clock_service'
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Add the possibility to use modules as trace data receivers. The functions
in the module have to be nifs as otherwise complex trace probes will be
very hard to handle (complex means trace probes for ports for example).
This commit changes the way that the ptab->tracer field works from always
being an immediate, to now be NIL if no tracer is present or else be
the tuple {TracerModule, TracerState} where TracerModule is an atom that
is later used to lookup the appropriate tracer callbacks to call and
TracerState is just passed to the tracer callback. The default process and
port tracers have been rewritten to use the new API.
This commit also changes the order which trace messages are delivered to the
potential tracer process. Any enif_send done in a tracer module may be delayed
indefinitely because of lock order issues. If a message is delayed any other
trace message send from that process is also delayed so that order is preserved
for each traced entity. This means that for some trace events (i.e. send/receive)
the events may come in an unintuitive order (receive before send) to the
trace receiver. Timestamps are taken when the trace message is generated so
trace messages from differented processes may arrive with the timestamp
out of order.
Both the erlang:trace and seq_trace:set_system_tracer accept the new tracer
module tracers and also the backwards compatible arguments.
OTP-10267
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perf counter is now part of the function pointer interface
and also the function returns the value instead of writing
to a memory buffer.
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Microstate accounting is a way to track which state the
different threads within ERTS are in. The main usage area
is to pin point performance bottlenecks by checking which
states the threads are in and then from there figuring out
why and where to optimize.
Since checking whether microstate accounting is on or off is
relatively expensive if done in a short loop only a few of the
states are enabled by default and more states can be enabled
through configure.
I've done some benchmarking and the overhead with it turned off
is not noticible and with it on it is a fraction of a percent.
If you enable the extra states, depending on the benchmark,
the ovehead when turned off is about 1% and when turned on
somewhere inbetween 5-15%.
OTP-12345
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