From 0386b99694ba4c3ab18048e7a57d46bc34201bfb Mon Sep 17 00:00:00 2001 From: Martin Quinson Date: Sun, 18 May 2014 20:33:40 +0200 Subject: [PATCH 1/1] further document the parmap mess. Next step should be refactoring/simplifying --- src/simix/smx_context_sysv.c | 73 +++++++++++++++++++++--------------- src/xbt/parmap.c | 10 ++--- 2 files changed, 47 insertions(+), 36 deletions(-) diff --git a/src/simix/smx_context_sysv.c b/src/simix/smx_context_sysv.c index c3e5ecac0f..7fc7f6f13d 100644 --- a/src/simix/smx_context_sysv.c +++ b/src/simix/smx_context_sysv.c @@ -240,8 +240,48 @@ static void smx_ctx_sysv_stop_parallel(smx_context_t context) smx_ctx_sysv_suspend_parallel(context); } -static void smx_ctx_sysv_suspend_parallel(smx_context_t context) -{ +/* 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. + */ +static void smx_ctx_sysv_runall_parallel(void) { +#ifdef CONTEXT_THREADS + sysv_threads_working = 0; + // parmap_apply ensures that every working thread get an index in the process_to_run array (through an atomic fetch_and_add), + // and runs the smx_ctx_sysv_resume_parallel function on that index + xbt_parmap_apply(sysv_parmap, (void_f_pvoid_t) smx_ctx_sysv_resume_parallel, + simix_global->process_to_run); +#else + xbt_die("You asked for a parallel execution, but you don't have any threads."); +#endif +} + +/* This function is in charge of running one particular simulated process on the current thread */ +static void smx_ctx_sysv_resume_parallel(smx_process_t simulated_process_to_run) { +#ifdef CONTEXT_THREADS + unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1); // what is my containing body? + xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id); // Store the number of my containing body in os-thread-specific area + smx_ctx_sysv_t worker_context = (smx_ctx_sysv_t)SIMIX_context_self(); // get my current soul + sysv_workers_context[worker_id] = worker_context; // write down that this soul is hosted in that body (for now) + ucontext_t* worker_stack = &worker_context->uc; // retrieves the system-level info that fuels this soul + + smx_context_t context = simulated_process_to_run->context; // That's the first soul that I should become + SIMIX_context_set_current(context); // write in simix that I switched my soul + swapcontext(worker_stack, &((smx_ctx_sysv_t) context)->uc); // actually do that using the relevant syscall + // No body runs that soul anymore at this point. Instead the current body took the soul of simulated process + // The simulated process wakes back after the call to "SIMIX_context_suspend(self->context);" within smx_process.c::SIMIX_process_yield() + + // From now on, the simulated processes will change their soul with the next soul to execute (in suspend_parallel, below). + // When nobody is to be executed in this scheduling round, the last simulated process will take back the initial soul of the current working thread +#endif +} + +/* This function is called when a simulated process wants to yield back to the maestro in a blocking simcall. + * This naturally occurs within SIMIX_context_suspend(self->context), called from SIMIX_process_yield() + * Actually, it does not really yield back to maestro, but into the next process that must be executed. + * If no one is to be executed, then it yields to the initial soul that was in this working thread (that was saved in resume_parallel). + */ +static void smx_ctx_sysv_suspend_parallel(smx_context_t context) { #ifdef CONTEXT_THREADS /* determine the next context */ smx_process_t next_work = xbt_parmap_next(sysv_parmap); // get the next soul to embody now @@ -267,32 +307,3 @@ static void smx_ctx_sysv_suspend_parallel(smx_context_t context) swapcontext(&((smx_ctx_sysv_t) context)->uc, next_stack); // get that next soul #endif } - -static void smx_ctx_sysv_resume_parallel(smx_process_t simulated_process_to_run) -{ -#ifdef CONTEXT_THREADS - unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1); // what is my containing body? - xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id); // Store the number of my containing body in os-thread-specific area - smx_ctx_sysv_t worker_context = (smx_ctx_sysv_t)SIMIX_context_self(); // get my current soul - sysv_workers_context[worker_id] = worker_context; // write down that this soul is hosted in that body (for now) - ucontext_t* worker_stack = &worker_context->uc; // retrieves the system-level info that fuels this soul - - smx_context_t context = simulated_process_to_run->context; // That's the first soul that I should become - SIMIX_context_set_current(context); // write in simix that I switched my soul - swapcontext(worker_stack, &((smx_ctx_sysv_t) context)->uc); // actually do that using the relevant syscall - // No body runs that soul anymore at this point. Instead the current body took the soul of simulated process - // The simulated process wakes back after the call to "SIMIX_context_suspend(self->context);" within smx_process.c::SIMIX_process_yield() - - // From now on, the simulated processes will change their soul with the next soul to execute (in suspend_parallel, above). - // When nobody is to be executed in this scheduling round, the last simulated process will take back the initial soul of the current working thread -#endif -} - -static void smx_ctx_sysv_runall_parallel(void) -{ -#ifdef CONTEXT_THREADS - sysv_threads_working = 0; - xbt_parmap_apply(sysv_parmap, (void_f_pvoid_t) smx_ctx_sysv_resume_parallel, - simix_global->process_to_run); -#endif -} diff --git a/src/xbt/parmap.c b/src/xbt/parmap.c index cdb6e916b6..1b0ab3d793 100644 --- a/src/xbt/parmap.c +++ b/src/xbt/parmap.c @@ -272,14 +272,14 @@ static void xbt_parmap_set_mode(xbt_parmap_t parmap, e_xbt_parmap_mode_t mode) */ void xbt_parmap_apply(xbt_parmap_t parmap, void_f_pvoid_t fun, xbt_dynar_t data) { - /* Assign resources to worker threads */ + /* Assign resources to worker threads (we are maestro here)*/ parmap->fun = fun; parmap->data = data; parmap->index = 0; - parmap->master_signal_f(parmap); - xbt_parmap_work(parmap); - parmap->master_wait_f(parmap); - XBT_DEBUG("Job done"); + parmap->master_signal_f(parmap); // maestro runs futex_wait to wake all the minions (the working threads) + xbt_parmap_work(parmap); // maestro works with its minions + parmap->master_wait_f(parmap); // When there is no more work to do, then maestro waits for the last minion to stop + XBT_DEBUG("Job done"); // ... and proceeds } /** -- 2.20.1