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OTP-14899
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Implementation of true asynchronous signaling between processes
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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The previously used message queue partitioned into two halves has been
replaced by a more general signal queue partitioned into three parts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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kernel: in the group added processing of 'EXIT' signal from shell
OTP-14991
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Short-circuit code:ensure_loaded for already-loaded modules
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* sverker/send-tick/OTP-14681:
kernel: Fix and improve send_tick logic
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This checks if the module is already loaded using erlang:module_loaded
before calling the code server. This should improve performance of the
call significantly since the case where module is already loaded is the
common one.
The change shouldn't cause any problems. It's worth noting that
code:ensure_modules_loaded already does a similar check.
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* raimo/stop-encouraging-v4-mapped/ERL-503/OTP-13716:
Stop translating V4MAPPED addresses
Stop returning V4MAPPED addresses
Implement function for IPv4-mapped IPv6 addresses
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* origin/hasse/kernel/rpc_doc_fix/OTP-10551:
kernel: Improve docs of rpc:multicall/5
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as workarounds to avoid blocking auto-connect,
which is now asynchronous in OTP-21.
Also changed old catch to more efficient try-catch.
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to replace DFLAGS_STRICT_ORDER_DELIVERY
and remove that compile time dependency.
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and remove use in dist_util:check_mandatory
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to a simple 'band' operation into ChosenFlags
and no need to remember old 'this_flags' and 'other_flags'.
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for kernel to ask erts about distribution flags
and keep this info in one place.
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No need to clear them as they cannot be set.
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or backslash on Windows.
Purpose: Prevent tricks to get hostile code running.
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* maint:
Updated OTP version
Update release notes
Update version numbers
kernel: Add os:cmd/2 with max_size option
# Conflicts:
# OTP_VERSION
# lib/kernel/doc/src/os.xml
# lib/kernel/src/os.erl
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* maint-20:
Updated OTP version
Update release notes
Update version numbers
erts: Add system_flags(erts_alloc,"+M?sbct *")
erts: Add age order first fit allocator strategies
erts: Refactor erl_ao_firstfit_alloc
erts: Add migration options "acnl" and "acfml"
kernel: Add os:cmd/2 with max_size option
erts: Add more stats for mbcs_pool
erts: Fix alloc_SUITE:migration
stdlib: Make ets_SUITE memory check try again
erts: Improve carrier pool search
erts: Improve alloc_SUITE:migration
erts: Refactor carrier dealloc migration
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the group leader is waiting data from IO driver
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Currently HiPE amd64 assumes the runtime system code is loaded into
the low 2G of the address space. However, this is not the case when
PIE is enabled, it is loaded into a random location. So trampolines
are required to call BIFs, and also we have first to load the address
of sse2_fnegate_mask to a regisiter before xorpd in fchs.
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* maint:
kernel: Correct contracts and a bug in group_history
stdlib: Correct contracts
dialyzer: Optimize handling of a lot of warnings
Conflicts:
lib/kernel/src/erl_boot_server.erl
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particularly slow erlc when compiler is hipe compiled.
hipe_unified_loader:load did not patch external call sites
and instead caused a double hipe mode switch per call.
hipe_unified_loader:load is only used
for early modules first loaded as beam
and by code:atomic_load and friends.
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OTP:13713: Add documentation and typespecs for inet:i/0
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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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* dgud/kernel/refc_sched_wall_time/OTP-11694:
test: spawn scheduler_wall_time flag holder
Turn on scheduler_wall_time in an alive process
Redirect system_flag(scheduler_wall_time,_) to kernel_refc
kernel: add a resource reference counter
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In general, the new NIF-based file routines are faster than the old
efile driver.
However, on some computers, building the entire OTP system is somewhat
slower. It turns out that it is because 'erlc' cheated by turning off
the IO thread pool (using '+A0') to avoid context switches between
scheduler threads and threads in the IO thread pool. The new file
routines perform IO on dirty IO threads, and there is (by intent) no
way to force the operations to occur on scheduler threads to avoid
the context switches
What we can do to is to use a small (4Kb) read-ahead buffer for files
opened for reading (only) in list mode (which is how the compiler
opens its input files). The buffering reduces the number of context
switches between scheduler threads and dirty IO threads. On my
computer that seems to slightly speed up building of the entire OTP
system.
The buffer should do no harm. The only potential for harm I can
think of is random access to a file opened in read mode, where
the read-ahead buffer could slightly decrease performance. That
does not seems to be a likely use case in practice, though.
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System resources/functionality may need to be reference counted
to be handled correctly when used or enabled/disabled from more
than one process or application.
It is easier to handle this in erlang code than in erts, so make a
process that deals with the housekeeping.
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This improves the latency of file operations as dirty schedulers
are a bit more eager to run jobs than async threads, and use a
single global queue rather than per-thread queues, eliminating the
risk of a job stalling behind a long-running job on the same thread
while other async threads sit idle.
There's no such thing as a free lunch though; the lowered latency
comes at the cost of increased busy-waiting which may have an
adverse effect on some applications. This behavior can be tweaked
with the +sbwt flag, but unfortunately it affects all types of
schedulers and not just dirty ones. We plan to add type-specific
flags at a later stage.
sendfile has been moved to inet_drv to lessen the effect of a nasty
race; the cooperation between inet_drv and efile has never been
airtight and the socket dying at the wrong time (Regardless of
reason) could result in fd aliasing. Moving it to the inet driver
makes it impossible to trigger this by closing the socket in the
middle of a sendfile operation, while still allowing it to be
aborted -- something that can't be done if it stays in the file
driver.
The race still occurs if the controlling process dies in the short
window between dispatching the sendfile operation and the dup(2)
call in the driver, but it's much less likely to happen now.
A proper fix is in the works.
--
Notable functional differences:
* The use_threads option for file:sendfile/5 no longer has any
effect.
* The file-specific DTrace probes have been removed. The same
effect can be achieved with normal tracing together with the
nif__entry/nif__return probes to track scheduling.
--
OTP-14256
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* maint:
Update HOWTO with wxWidgets build examples
https should be mapped to url and not seealso
Update kernel appup for OTP-20.2
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* siri/appups-20.2:
Update kernel appup for OTP-20.2
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d8d07a7593d811 that added the to_dis option to the compiler no longer
works when merged to master. That is because of 79f28cfd8df1b7
that removed some unused code in erts_debug.
Fix this by adding a new function erts_debug:dis_to_file/2 and
use it from compile module where we have access to the filename
(in beam_listing we only have an opened file).
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Conflicts:
lib/compiler/src/beam_listing.erl
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