* Use now crosstraffic keyword instead of the terribly missleading
fullduplex keyword. Use --cfg=network/crosstraffic:1. This is
activated by default now in the current default model.
-
+
+ Simix:
+ * Stabilize the parallel execution mode of user contexts
+ * Introduce configuration variables to control parallel execution:
+ - contexts/synchro: Synchronization mode to use when running
+ contexts in parallel (either futex, posix or busy_wait)
+ - contexts/parallel_threshold: Minimal number of user contexts
+ to be run in parallel (raw contexts only)
+
SimDag:
* Performance boost by using a swag internally to compute the set of
tasks that are finished and should constitute the return value of
void MC_assert(int prop);
\endverbatim
+\section options_virt User process virtualization options
+
+\subsection options_virt_factory Selecting the virtualization factory
+
+In SimGrid, the user code is virtualized in a specific mecanism
+allowing the simulation kernel to control its execution: when a user
+process requires a blocking action (such as sending a message), it is
+interrupted, and only gets released when the simulated clock reaches
+the point where the blocking operation is done.
+
+In SimGrid, the containers in which user processes are virtualized are
+called contexts. Several context factory are provided, and you can
+select the one you want to use with the \b contexts/factory
+configuration variable. Some of the following may not exist on your
+machine because of portability issues. In any case, the default one
+should be the most effcient one (please report bugs if the
+auto-detection fails for you). They are sorted here from the slowest
+to the most effient:
+ - \b thread: very slow factory using full featured threads (either
+ ptheads or windows native threads)
+ - \b ucontext: fast factory using System V contexts (or a portability
+ layer of our own on top of Windows fibers)
+ - \b raw: amazingly fast factory using a context switching mecanism
+ of our own, directly implemented in assembly (only available for x86
+ and amd64 platforms for now)
+
+The only reason to change this setting is when the debuging tools get
+fooled by the optimized context factories. Threads are the most
+debugging-friendly contextes.
+
+\subsection options_virt_stacksize Adapting the used stack size
+
+(this only works if you use ucontexts or raw context factories)
+
+Each virtualized used process is executed using a specific system
+stack. The size of this stack has a huge impact on the simulation
+scalability, but its default value is rather large. This is because
+the error messages that you get when the stack size is too small are
+rather disturbing: this leads to stack overflow (overwriting other
+stacks), leading to segfaults with corrupted stack traces.
+
+If you want to push the scalability limits of your code, you really
+want to reduce the \b contexts/stack_size variable. Its default value
+is 128 (in Kib), while our Chord simulation works with stacks as small
+as 16 Kib, for example.
+
+\subsection options_virt_parallel Running user code in parallel
+
+Parallel execution of the user code is only considered stable in
+SimGrid v3.7 and higher. It is described in
+<a href="http://hal.inria.fr/inria-00602216/">INRIA RR-7653</a>.
+
+If you are using the \c ucontext or \c raw context factories, you can
+request to execute the user code in parallel. Several threads are
+launched, each of them handling as much user contexts at each run. To
+actiave this, set the \b contexts/nthreads variable to the amount of
+core that you have in your computer.
+
+Even if you asked several worker threads using the previous option,
+you can request to start the parallel execution (and pay the
+associated synchronization costs) only if the potential parallelism is
+large enough. For that, set the \b contexts/parallel_threshold
+variable to the minimal amount of user contexts needed to start the
+parallel execution. In any given simulation round, if that amount is
+not reached, the contexts will be run sequentially directly by the
+main thread (thus saving the synchronization costs). Note that this
+option is mainly useful when the grain of the user code is very fine,
+because our synchronization is now very efficient.
+
+When parallel execution is activated, you can choose the
+synchronization schema used with the \b contexts/synchro variable,
+which value is either:
+ - \b futex: ultra optimized synchronisation schema, based on futexes
+ (fast user-mode mutexes), and thus only available on Linux systems.
+ This is the default mode when available.
+ - \b posix: slow but portable synchronisation using only POSIX
+ primitives.
+ - \b busy_wait: not really a synchronisation: the worker threads
+ constantly request new contexts to execute. It should be the most
+ efficient synchronisation schema, but it loads all the cores of your
+ machine for no good reason. You probably prefer the other less
+ eager schemas.
+
+
+
\section options_generic Various generic configuration variables
\section options_generic_path XML file inclusion path
\section options_index Index of all existing variables
+- \c contexts/factory: \ref options_virt_factory
+- \c contexts/nthreads: \ref options_virt_parallel
+- \c contexts/parallel_threshold: \ref options_virt_parallel
+- \c contexts/stack_size: \ref options_virt_stacksize
+- \c contexts/synchro: \ref options_virt_parallel
+
+
- \c cpu/maxmin_selective_update: \ref options_model_optim
- \c cpu/model: \ref options_model_select
- \c cpu/optim: \ref options_model_optim
/* a fast and simple context switching library */
-/* Copyright (c) 2009, 2010. The SimGrid Team.
+/* Copyright (c) 2009 - 2011. The SimGrid Team.
* All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
if (nb_threads > 1) {
#ifndef CONTEXT_THREADS
- THROWF(arg_error, 0, "No thread support for parallel context execution");
+ THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
#endif
}
sprintf(p,
".\n (use 'help' as a value to see the long description of each model)");
default_value = xbt_strdup("Cas01");
- xbt_cfg_register(&_surf_cfg_set,
- "cpu/model", description, xbt_cfgelm_string,
+ xbt_cfg_register(&_surf_cfg_set, "cpu/model", description, xbt_cfgelm_string,
&default_value, 1, 1, &_surf_cfg_cb__cpu_model, NULL);
sprintf(description,
sprintf(p,
".\n (use 'help' as a value to see the long description of each optimization mode)");
default_value = xbt_strdup("Lazy");
- xbt_cfg_register(&_surf_cfg_set,
- "cpu/optim", description, xbt_cfgelm_string,
+ xbt_cfg_register(&_surf_cfg_set, "cpu/optim", description, xbt_cfgelm_string,
&default_value, 1, 1, &_surf_cfg_cb__optimization_mode, NULL);
sprintf(description,
sprintf(p,
".\n (use 'help' as a value to see the long description of each model)");
default_value = xbt_strdup("LV08");
- xbt_cfg_register(&_surf_cfg_set,
- "network/model", description, xbt_cfgelm_string,
+ xbt_cfg_register(&_surf_cfg_set, "network/model", description, xbt_cfgelm_string,
&default_value, 1, 1, &_surf_cfg_cb__network_model,
NULL);
sprintf(p,
".\n (use 'help' as a value to see the long description of each optimization mode)");
default_value = xbt_strdup("Lazy");
- xbt_cfg_register(&_surf_cfg_set,
- "network/optim", description, xbt_cfgelm_string,
+ xbt_cfg_register(&_surf_cfg_set, "network/optim", description, xbt_cfgelm_string,
&default_value, 1, 1, &_surf_cfg_cb__optimization_mode, NULL);
sprintf(description,
sprintf(p,
".\n (use 'help' as a value to see the long description of each model)");
default_value = xbt_strdup("default");
- xbt_cfg_register(&_surf_cfg_set,
- "workstation/model", description, xbt_cfgelm_string,
+ xbt_cfg_register(&_surf_cfg_set, "workstation/model", description, xbt_cfgelm_string,
&default_value, 1, 1,
&_surf_cfg_cb__workstation_model, NULL);
/* stack size of contexts in Ko */
default_value_int = 128;
xbt_cfg_register(&_surf_cfg_set, "contexts/stack_size",
- "Stack size of contexts in Ko (ucontext or raw only)",
+ "Stack size of contexts in Kib (ucontext or raw only)",
xbt_cfgelm_int, &default_value_int, 1, 1,
_surf_cfg_cb_context_stack_size, NULL);
/* number of parallel threads for user processes */
default_value_int = 1;
xbt_cfg_register(&_surf_cfg_set, "contexts/nthreads",
- "Number of parallel threads for user contexts (EXPERIMENTAL)",
+ "Number of parallel threads used to execute user contexts",
xbt_cfgelm_int, &default_value_int, 1, 1,
_surf_cfg_cb_contexts_nthreads, NULL);
/* minimal number of user contexts to be run in parallel */
- default_value_int = 1;
+ default_value_int = 2;
xbt_cfg_register(&_surf_cfg_set, "contexts/parallel_threshold",
"Minimal number of user contexts to be run in parallel (raw contexts only)",
xbt_cfgelm_int, &default_value_int, 1, 1,
/* minimal number of user contexts to be run in parallel */
default_value = xbt_strdup("futex");
- xbt_cfg_register(&_surf_cfg_set, "contexts/parallel_mode",
- "Synchronization mode to use when running contexts in parallel",
+ xbt_cfg_register(&_surf_cfg_set, "contexts/synchro",
+ "Synchronization mode to use when running contexts in parallel (either futex, posix or busy_wait)",
xbt_cfgelm_string, &default_value, 1, 1,
_surf_cfg_cb_contexts_parallel_mode, NULL);
