-/* Copyright (c) 2009-2018. The SimGrid Team. All rights reserved. */
+/* Copyright (c) 2009-2019. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
#include "xbt/parmap.hpp"
#include "src/kernel/context/ContextSwapped.hpp"
-#include "src/kernel/context/ContextUnix.hpp" // FIXME: temporary reverse import
#ifdef _WIN32
#include <malloc.h>
namespace kernel {
namespace context {
-/* Parallel execution */
-simgrid::xbt::Parmap<smx_actor_t>* SwappedContext::parmap_;
-std::atomic<uintptr_t> SwappedContext::threads_working_; /* number of threads that have started their work */
+/* rank of the execution thread */
thread_local uintptr_t SwappedContext::worker_id_; /* thread-specific storage for the thread id */
-std::vector<SwappedContext*> SwappedContext::workers_context_; /* space to save the worker's context in each thread */
-SwappedContextFactory::SwappedContextFactory(std::string name)
- : ContextFactory(name), parallel_(SIMIX_context_is_parallel())
-{
- SwappedContext::set_maestro(nullptr);
- SwappedContext::initialize(parallel_);
-}
-SwappedContextFactory::~SwappedContextFactory()
-{
- SwappedContext::finalize();
-}
-/** Maestro wants to run all ready actors */
-void SwappedContextFactory::run_all()
-{
- /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
- * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
- * for the ones of the simulated processes that must run.
- */
- if (parallel_) {
- SwappedContext::threads_working_ = 0;
-
- // We lazily create the parmap so that all options are actually processed when doing so.
- if (SwappedContext::parmap_ == nullptr)
- SwappedContext::parmap_ =
- new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
-
- // Usually, Parmap::apply() executes the provided function on all elements of the array.
- // Here, the executed function does not return the control to the parmap before all the array is processed:
- // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
- // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
- // It only yields back to worker_context when the work array is exhausted.
- // - So, resume() is only launched from the parmap for the first job of each minion.
- SwappedContext::parmap_->apply(
- [](smx_actor_t process) {
- SwappedContext* context = static_cast<SwappedContext*>(process->context_);
- context->resume();
- },
- simix_global->process_to_run);
- } else { // sequential execution
- if (simix_global->process_to_run.empty())
- return;
- smx_actor_t first_actor = simix_global->process_to_run.front();
- process_index_ = 1;
- /* execute the first actor; it will chain to the others when using suspend() */
- static_cast<SwappedContext*>(first_actor->context_)->resume();
- }
-}
-
-void SwappedContext::initialize(bool parallel)
+SwappedContextFactory::SwappedContextFactory() : ContextFactory(), parallel_(SIMIX_context_is_parallel())
{
parmap_ = nullptr; // will be created lazily with the right parameters if needed (ie, in parallel)
- if (parallel) {
- workers_context_.clear();
- workers_context_.resize(SIMIX_context_get_nthreads(), nullptr);
- }
+ workers_context_.clear();
+ workers_context_.resize(parallel_ ? SIMIX_context_get_nthreads() : 1, nullptr);
}
-
-void SwappedContext::finalize()
+SwappedContextFactory::~SwappedContextFactory()
{
delete parmap_;
parmap_ = nullptr;
workers_context_.clear();
}
-SwappedContext* SwappedContext::maestro_context_ = nullptr;
-
SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process,
SwappedContextFactory* factory)
: Context(std::move(code), cleanup_func, process), factory_(factory)
{
+ // Save maestro (=context created first) in preparation for run_all
+ if (factory_->workers_context_[0] == nullptr)
+ factory_->workers_context_[0] = this;
+
if (has_code()) {
if (smx_context_guard_size > 0 && not MC_is_active()) {
xbt_free(stack_);
}
-/** Maestro wants to yield back to a given actor */
+void* SwappedContext::get_stack()
+{
+ return stack_;
+}
+
+void SwappedContext::stop()
+{
+ Context::stop();
+ /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
+ throw StopRequest();
+}
+
+/** Maestro wants to run all ready actors */
+void SwappedContextFactory::run_all()
+{
+ /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
+ * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
+ * for the ones of the simulated processes that must run.
+ */
+ if (parallel_) {
+ threads_working_ = 0;
+
+ // We lazily create the parmap so that all options are actually processed when doing so.
+ if (parmap_ == nullptr)
+ parmap_ = new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
+
+ // Usually, Parmap::apply() executes the provided function on all elements of the array.
+ // Here, the executed function does not return the control to the parmap before all the array is processed:
+ // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
+ // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
+ // It only yields back to worker_context when the work array is exhausted.
+ // - So, resume() is only launched from the parmap for the first job of each minion.
+ parmap_->apply(
+ [](smx_actor_t process) {
+ SwappedContext* context = static_cast<SwappedContext*>(process->context_);
+ context->resume();
+ },
+ simix_global->process_to_run);
+ } else { // sequential execution
+ if (simix_global->process_to_run.empty())
+ return;
+
+ /* maestro is already saved in the first slot of workers_context_ */
+ smx_actor_t first_actor = simix_global->process_to_run.front();
+ process_index_ = 1;
+ /* execute the first actor; it will chain to the others when using suspend() */
+ static_cast<SwappedContext*>(first_actor->context_)->resume();
+ }
+}
+
+/** Maestro wants to yield back to a given actor, so awake it on the current thread
+ *
+ * In parallel, it is only applied to the N first elements of the parmap array,
+ * where N is the amount of worker threads in the parmap.
+ * See SwappedContextFactory::run_all for details.
+ */
void SwappedContext::resume()
{
if (factory_->parallel_) {
- THROW_IMPOSSIBLE;
+ // Save the thread number (my body) in an os-thread-specific area
+ worker_id_ = factory_->threads_working_.fetch_add(1, std::memory_order_relaxed);
+ // Save my current soul (either maestro, or one of the minions) in a permanent area
+ SwappedContext* worker_context = static_cast<SwappedContext*>(self());
+ factory_->workers_context_[worker_id_] = worker_context;
+ // Switch my soul and the actor's one
+ Context::set_current(this);
+ worker_context->swap_into(this);
+ // No body runs that soul anymore at this point, but it is stored in a safe place.
+ // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
} else { // sequential execution
- // Maestro is always the calling thread of this function (ie, self() == maestro)
SwappedContext* old = static_cast<SwappedContext*>(self());
Context::set_current(this);
old->swap_into(this);
}
}
-/** The actor wants to yield back to maestro */
+/** The actor wants to yield back to maestro, because it is blocked in a simcall (ie in SIMIX_process_yield())
+ *
+ * Actually, it does not really yield back to maestro, but directly into the next executable actor.
+ *
+ * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
+ * on the few first elements of the array, but it saves a lot of context switches back to maestro,
+ * and directly forth to the next executable actor.
+ */
void SwappedContext::suspend()
{
if (factory_->parallel_) {
- THROW_IMPOSSIBLE;
+ // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
+ boost::optional<smx_actor_t> next_work = factory_->parmap_->next();
+ SwappedContext* next_context;
+ if (next_work) {
+ // There is a next soul to embody (ie, another executable actor)
+ XBT_DEBUG("Run next process");
+ next_context = static_cast<SwappedContext*>(next_work.get()->context_);
+ } else {
+ // All actors were run, go back to the parmap context
+ XBT_DEBUG("No more actors to run");
+ // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
+ next_context = factory_->workers_context_[worker_id_];
+ // When given that soul, the body will wait for the next scheduling round
+ }
+
+ // Get the next soul to run, either from another actor or the initial minion's one
+ Context::set_current(next_context);
+ this->swap_into(next_context);
+
} else { // sequential execution
/* determine the next context */
SwappedContext* next_context;
if (i < simix_global->process_to_run.size()) {
/* Actually swap into the next actor directly without transiting to maestro */
- XBT_DEBUG("Run next process");
+ XBT_DEBUG("Run next actor");
next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
} else {
/* all processes were run, actually return to maestro */
- XBT_DEBUG("No more process to run");
- next_context = static_cast<SwappedContext*>(get_maestro());
+ XBT_DEBUG("No more actors to run");
+ next_context = factory_->workers_context_[0];
}
Context::set_current(next_context);
this->swap_into(next_context);
}
}
-void SwappedContext::stop()
-{
- Context::stop();
- throw StopRequest();
-}
-
} // namespace context
} // namespace kernel
} // namespace simgrid
