X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/0c675d990c2f0c5060cf49c746a83db99949ef2c..df6fdd5cc2f67e7097e287bf8359809c1f943b08:/doc/doxygen/options.doc diff --git a/doc/doxygen/options.doc b/doc/doxygen/options.doc index 98f91ccf2b..9fb339929b 100644 --- a/doc/doxygen/options.doc +++ b/doc/doxygen/options.doc @@ -316,7 +316,7 @@ setting on regular (less constrained) scenarios so it is off by default. \subsubsection options_model_network_gamma Maximal TCP window size The analytical models need to know the maximal TCP window size to take -the TCP congestion mechanism into account. This is set to 20000 by +the TCP congestion mechanism into account. This is set to 4194304 by default, but can be changed using the \b network/TCP-gamma item. On linux, this value can be retrieved using the following @@ -654,7 +654,7 @@ the slowest to the most efficient: - \b ucontext: fast factory using System V contexts (Linux and FreeBSD only) - \b boost: This uses the [context implementation](http://www.boost.org/doc/libs/1_59_0/libs/context/doc/html/index.html) of the boost library for a performance that is comparable to our - raw implementation.\nInstall the relevant library (e.g. with the + raw implementation.\n Install the relevant library (e.g. with the libboost-contexts-dev package on Debian/Ubuntu) and recompile SimGrid. Note that our implementation is not compatible with recent implementations of the library, and it will be hard to fix this since @@ -998,49 +998,21 @@ of counters, the "default" set. \subsection options_smpi_privatization smpi/privatization: Automatic privatization of global variables -MPI executables are usually meant to be executed in separated processes, but SMPI is -executed in only one process. Global variables from executables will be placed -in the same memory zone and shared between processes, causing intricate bugs. -Several options are possible to avoid this, as described in the main -SMPI publication. -SimGrid provides two ways of automatically privatizing the globals, -and this option allows to choose between them. - - - no (default): Do not automatically privatize variables. - - mmap or yes: Runtime automatic switching of the data segments.\n - SMPI stores a copy of each global data segment for each process, - and at each context switch replaces the actual data with its copy - from the right process. No copy actually occures as this mechanism - uses mmap for efficiency. As such, it is for now limited to - systems supporting this functionnality (all Linux and most BSD).\n - Another limitation is that SMPI only accounts for global variables - defined in the executable. If the processes use external global - variables from dynamic libraries, they won't be switched - correctly. The easiest way to solve this is to statically link - against the library with these globals (but you should never - statically link against the simgrid library itself). - - dlopen: Link multiple times against the binary.\n - SMPI loads several copy of the same binary in memory, resulting in - the natural duplication global variables. Since the dynamic linker - refuses to link the same file several times, the binary is copied - in a temporary file before being dl-loaded (it is erased right - after loading).\n - Note that this feature is somewhat experimental at time of writing - (v3.16) but seems to work.\n - This approach greatly speeds up the context switching, down to - about 40 CPU cycles with our raw contextes, instead of requesting - several syscalls with the \c mmap approach. Another advantage is - that it permits to run the SMPI contexts in parallel, which is - obviously not possible with the \c mmap approach.\n - Further work may be possible to alleviate the memory and disk - overconsumption. It seems that we could - punch holes - in the files before dl-loading them to remove the code and - constants, and mmap these area onto a unique copy. This require - to understand the ELF layout of the file, but would - reduce the disk- and memory- usage to the bare minimum. In - addition, this would reduce the pressure on the CPU caches (in - particular on instruction one). +MPI executables are usually meant to be executed in separated +processes, but SMPI is executed in only one process. Global variables +from executables will be placed in the same memory zone and shared +between processes, causing intricate bugs. Several options are +possible to avoid this, as described in the main +SMPI publication and in +the @ref SMPI_what_globals "SMPI documentation". SimGrid provides two +ways of automatically privatizing the globals, and this option allows +to choose between them. + + - no (default when not using smpirun): Do not automatically privatize variables. + Pass \c -no-privatize to smpirun to disable this feature. + - dlopen or yes (default when using smpirun): Link multiple times against the binary. + - mmap (slower, but maybe somewhat more stable): + Runtime automatic switching of the data segments. \warning This configuration option cannot be set in your platform file. You can only @@ -1272,10 +1244,10 @@ is registered and will clean up some variables and terminate/cleanup the tracing TODO: Add when this should be used. -\subsection options_generic_path XML file inclusion path +\subsection options_generic_path Profile files' search path It is possible to specify a list of directories to search into for the -\ tag in XML files by using the \b path configuration +trace files (see @ref pf_trace) by using the \b path configuration item. To add several directory to the path, set the configuration item several times, as in \verbatim --cfg=path:toto --cfg=path:tutu @@ -1292,7 +1264,7 @@ when \b verbose-exit is set to 0 (it is to 1 by default). \subsection options_exception_cutpath Truncate local path from exception backtrace \verbatim ---cfg=exceptions/cutpath:1 +--cfg=exception/cutpath:1 \endverbatim This configuration option is used to remove the path from the