X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/15f9e0adbd11d2a0736440004a2f71ef9cfccab8..080e391e51390f2739098295d391680e05a6ca93:/src/kernel/context/ContextSwapped.cpp diff --git a/src/kernel/context/ContextSwapped.cpp b/src/kernel/context/ContextSwapped.cpp index 2d53c8e4cf..b550205e99 100644 --- a/src/kernel/context/ContextSwapped.cpp +++ b/src/kernel/context/ContextSwapped.cpp @@ -1,4 +1,4 @@ -/* 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. */ @@ -11,7 +11,6 @@ #include "xbt/parmap.hpp" #include "src/kernel/context/ContextSwapped.hpp" -#include "src/kernel/context/ContextUnix.hpp" // FIXME: temporary reverse import #ifdef _WIN32 #include @@ -35,77 +34,23 @@ namespace simgrid { namespace kernel { namespace context { -/* Parallel execution */ -simgrid::xbt::Parmap* SwappedContext::parmap_; -std::atomic 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::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(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(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(first_actor->context_)->resume(); - } -} - -void SwappedContext::initialize(bool 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 code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process, SwappedContextFactory* factory) : Context(std::move(code), cleanup_func, process), factory_(factory) @@ -189,24 +134,118 @@ SwappedContext::~SwappedContext() xbt_free(stack_); } -/** Maestro wants to yield back to a given actor */ +void SwappedContext::set_maestro(SwappedContext* ctx) +{ + if (factory_->threads_working_ == 0) // Don't save the soul of minions, only the one of maestro + factory_->workers_context_[0] = ctx; +} + +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(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(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(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(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(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 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(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; @@ -215,24 +254,18 @@ void SwappedContext::suspend() 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(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(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