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* bjorn/erts/persistent_terms/OTP-14669:
Implement a tab for persistent terms in crashdump viewer
Add tests of persistent terms for crashdump_viewer
Add a persistent term storage
Refactor releasing of literals
Extend the sharing-preserving routines to optionally copy literals
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Persistent terms are useful for storing Erlang terms that are never
or infrequently updated. They have the following advantages:
* Constant time access. A persistent term is not copied when it is
looked up. The constant factor is lower than for ETS, and no locks
are taken when looking up a term.
* Persistent terms are not copied in garbage collections.
* There is only ever one copy of a persistent term (until it is
deleted). That makes them useful for storing configuration data
that needs to be easily accessible by all processes.
Persistent terms have the following drawbacks:
* Updates are expensive. The hash table holding the keys for the
persistent terms are updated whenever a persistent term is added,
updated or deleted.
* Updating or deleting a persistent term triggers a "global GC", which
will schedule a heap scan of all processes to search the heap of all
processes for the deleted term. If a process still holds a reference
to the deleted term, the process will be garbage collected and the
term copied to the heap of the process. This global GC can make the
system less responsive for some time.
Three BIFs (implemented in C in the emulator) is the entire
interface to the persistent term functionality:
* put(Key, Value) to store a persistent term.
* get(Key) to look up a persistent term.
* erase(Key) to delete a persistent term.
There are also two additional BIFs to obtain information about
persistent terms:
* info() to return a map with information about persistent terms.
* get() to return a list of a {Key,Value} tuples for all persistent
terms. (The values are not copied.)
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The removal set now uses a red-black tree instead of an array on
large inputs, decreasing runtime complexity from `n*n` to
`n*log(n)`. It will also exit early when there are no more items
left in the removal set, drastically improving performance and
memory use when the items to be removed are present near the head
of the list.
This got a lot more complicated than before as the overhead of
always using a red-black tree was unacceptable when either of the
inputs were small, but this compromise has okay-to-decent
performance regardless of input size.
Co-authored-by: Dmytro Lytovchenko <[email protected]>
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Communication between Erlang processes has conceptually always been
performed through asynchronous signaling. The runtime system
implementation has however previously preformed most operation
synchronously. In a system with only one true thread of execution, this
is not problematic (often the opposite). In a system with multiple threads
of execution (as current runtime system implementation with SMP support)
it becomes problematic. This since it often involves locking of structures
when updating them which in turn cause resource contention. Utilizing
true asynchronous communication often avoids these resource contention
issues.
The case that triggered this change was contention on the link lock due
to frequent updates of the monitor trees during communication with a
frequently used server. The signal order delivery guarantees of the
language makes it hard to change the implementation of only some signals
to use true asynchronous signaling. Therefore the implementations
of (almost) all signals have been changed.
Currently the following signals have been implemented as true
asynchronous signals:
- Message signals
- Exit signals
- Monitor signals
- Demonitor signals
- Monitor triggered signals (DOWN, CHANGE, etc)
- Link signals
- Unlink signals
- Group leader signals
All of the above already defined as asynchronous signals in the
language. The implementation of messages signals was quite
asynchronous to begin with, but had quite strict delivery constraints
due to the ordering guarantees of signals between a pair of processes.
The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts
that service all kinds of signals. More details regarding the signal
queue can be found in comments in the erl_proc_sig_queue.h file.
The monitor and link implementations have also been completely replaced
in order to fit the new asynchronous signaling implementation as good
as possible. More details regarding the new monitor and link
implementations can be found in the erl_monitor_link.h file.
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putenv(3) and friends aren't thread-safe regardless of how you slice
it; a global lock around all environment operations (like before)
keeps things safe as far as our own operations go, but we have
absolutely no control over what libc or a library dragged in by a
driver/NIF does -- they're free to call getenv(3) or putenv(3)
without honoring our lock.
This commit solves this by setting up an "emulated" environment which
can't be touched without going through our interfaces. Third-party
libraries can still shoot themselves in the foot but benign uses of
os:putenv/2 will no longer risk crashing the emulator.
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When finalizing outgoing distribution messages
we transcode them into using tuple fallbacks if the
receiver does not support bitstrings and export-funs.
This can only happen if the message was first encoded toward
a pending connection when the receiver was unknown.
It's an optimistic approach optmimized for modern beam nodes,
that expect real bitstrings and funs (since <R13).
Only erl_interface/jinterface lack this support.
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* maint:
Bump version of crash dumps to 0.4
Verify that binaries of different sizes are dumped correctly
Don't dump literal areas that are not referenced at all
Dump literals separately to avoid incomplete heap data
Implement dumping of maps in crash dumps
Buffer writing of crash dumps
Conflicts:
erts/emulator/beam/erl_alloc.types
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* rickard/null-chars/ERL-370/OTP-14543:
Don't allow null chars in various strings
Conflicts:
erts/emulator/beam/erl_alloc.types
erts/preloaded/ebin/erlang.beam
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Various places that now reject null chars inside strings
- Primitive file operations reject it in filenames.
- Primitive environment variable operations reject it in
names and values.
- os:cmd() reject it in its input.
Also '=' characters are rejected by primitive environment
variable operations in environment variable names.
Documentation has been updated to document null characters
in these types of data as invalid. Currently these operations
accept null chars at the end of strings, but that will change
in the future.
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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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This allows us to enable/disable lock counting at will, and greatly improves
the performance of erts_debug:lock_counters/1 since we no longer have to
worry about the lock counters "dying" while we're enumerating them.
OTP-14412
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* sverker/hipe-long-lived:
Make hipe_bifs:alloc_data/3 pad addr to alignment
erts: Change HIPE allocations from sys_alloc
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to long lived, short lived and native stack.
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Conflicts:
erts/emulator/beam/erl_binary.h
erts/emulator/beam/erl_monitors.c
erts/emulator/beam/erl_nif.c
erts/emulator/beam/global.h
erts/emulator/test/nif_SUITE_data/nif_SUITE.c
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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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The support is somewhat primitive, since it is determined at
call time if trace on return or exception should be sent.
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* rickard/new-purge-strategy/OTP-13833:
Fix reclaim of literal areas
Conflicts:
erts/emulator/beam/beam_bif_load.c
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Ensure that we cannot get any dangling pointers into code that
has been purged. This is done by a two phase purge. At first
phase all fun entries pointing into the code to purge are marked
for purge. All processes trying to call these funs will be suspended
and by this we avoid getting new direct references into the code.
When all processes has been checked, these processes are resumed.
The new purge strategy now also completely ignore the existence of
indirect references to the code (funs). If such exist, they will
cause bad fun exceptions to the caller, but will not prevent a
soft purge or cause a kill of a process having such live references
during a hard purge. This since it is impossible to give any
guarantees that no processes in the system have such indirect
references. Even when the system is completely clean from such
references, new ones can appear via distribution and/or disk.
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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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* lukas/erts/non-smp-debug-fixes/OTP-13047:
erts: Fix incorrect non-smp debug assert
erts: std_alloc is not thread safe on non-smp
Conflicts:
erts/emulator/beam/erl_alloc_util.c
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that uses its own super carrier (erts_exec_mmapper)
to guarantee low addressed and executable memory (PROT_EXEC).
Currently only used on x86_64 that needs low memory
for HiPE/AMD64's small code model.
By initializing erts_exec_mapper early we secure
its low memory area before erts_literal_mmapper might
steal it.
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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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* henrik/update-copyrightyear:
update copyright-year
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that could hang if concurrent deallocations was initiated.
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Conflicts:
erts/emulator/beam/erl_alloc.types
erts/emulator/beam/erl_bif_info.c
erts/emulator/beam/erl_process.c
erts/preloaded/ebin/erts_internal.beam
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This commit implements erts_internal:system_check(schedulers) with the
intent of a basic responsiveness test check of the schedulers.
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LONG_LIVED is not thread safe on non-smp and
can only be used by scheduler.
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