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 The previously used message queue partitioned into two halves has been replaced by a more general signal queue partitioned into three parts that service all kinds of signals.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.
* maint: Update primary bootstrap Conflicts: bootstrap/bin/start.boot bootstrap/bin/start_clean.boot bootstrap/lib/compiler/ebin/beam_asm.beam bootstrap/lib/compiler/ebin/beam_jump.beam bootstrap/lib/compiler/ebin/beam_listing.beam bootstrap/lib/compiler/ebin/beam_type.beam bootstrap/lib/compiler/ebin/beam_validator.beam bootstrap/lib/compiler/ebin/compile.beam bootstrap/lib/compiler/ebin/core_pp.beam bootstrap/lib/compiler/ebin/v3_codegen.beam bootstrap/lib/compiler/ebin/v3_kernel_pp.beam bootstrap/lib/kernel/ebin/dist_util.beam bootstrap/lib/kernel/ebin/error_logger.beam bootstrap/lib/kernel/ebin/erts_debug.beam bootstrap/lib/kernel/ebin/group_history.beam bootstrap/lib/kernel/ebin/hipe_unified_loader.beam bootstrap/lib/kernel/ebin/kernel.app bootstrap/lib/kernel/ebin/os.beam bootstrap/lib/kernel/ebin/user.beam bootstrap/lib/stdlib/ebin/array.beam bootstrap/lib/stdlib/ebin/dets.beam bootstrap/lib/stdlib/ebin/edlin.beam bootstrap/lib/stdlib/ebin/erl_lint.beam bootstrap/lib/stdlib/ebin/ets.beam bootstrap/lib/stdlib/ebin/filelib.beam bootstrap/lib/stdlib/ebin/filename.beam bootstrap/lib/stdlib/ebin/gen_statem.beam bootstrap/lib/stdlib/ebin/lib.beam bootstrap/lib/stdlib/ebin/otp_internal.beam bootstrap/lib/stdlib/ebin/qlc.beam bootstrap/lib/stdlib/ebin/shell.beam bootstrap/lib/stdlib/ebin/stdlib.appup bootstrap/lib/stdlib/ebin/string.beam bootstrap/lib/stdlib/ebin/unicode_util.beam
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
* dgud/dot_erlang/OTP-14439: fixup! Do not load .erlang from current dir erlc: Do not load .erlang escript: Do not load .erlang dialyzer: Do not load .erlang reltool: Add no_dot_erlang bootfiles Enable usage of no_dot_erlang in bootstrap Do not load .erlang from current dir