X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fruntime_control.xml;h=22ca59dcd25b1b1f0551bc427d8c00828b69072c;hb=4df9f0ee56ae232e1cf2f9531205af0dd916b496;hp=2b16234496a254dbcba699bb000f4c7cc50e0b42;hpb=f2b113c66ee688dc4249098c08a3dfab93b99f1d;p=ghc-hetmet.git diff --git a/docs/users_guide/runtime_control.xml b/docs/users_guide/runtime_control.xml index 2b16234..22ca59d 100644 --- a/docs/users_guide/runtime_control.xml +++ b/docs/users_guide/runtime_control.xml @@ -10,7 +10,8 @@ code and then links it with a non-trivial runtime system (RTS), which handles storage management, profiling, etc. - You have some control over the behaviour of the RTS, by giving + If you set the -rtsopts flag appropriately when linking, + you have some control over the behaviour of the RTS, by giving special command-line arguments to your program. When your Haskell program starts up, its RTS extracts @@ -48,8 +49,8 @@ wraparound in the counters is your fault!) - Giving a +RTS -f - RTS option option + Giving a +RTS -? + RTS option option will print out the RTS options actually available in your program (which vary, depending on how you compiled). @@ -61,14 +62,16 @@ +RTS -M128m -RTS to the command line. - + Setting global RTS options RTS optionsfrom the environment environment variablefor setting RTS options - RTS options are also taken from the environment variable + If the -rtsopts flag is set to + something other than none when linking, + RTS options are also taken from the environment variable GHCRTSGHCRTS . For example, to set the maximum heap size to 128M for all GHC-compiled programs (using an @@ -128,6 +131,15 @@ things like ctrl-C. This option is primarily useful for when you are using the Haskell code as a DLL, and want to set your own signal handlers. + + Note that even + with , the RTS + interval timer signal is still enabled. The timer signal + is either SIGVTALRM or SIGALRM, depending on the RTS + configuration and OS capabilities. To disable the timer + signal, use the -V0 RTS option (see + above). + @@ -413,22 +425,88 @@ - size + size RTS option - stack, minimum size + stack, initial size - [Default: 1k] Set the initial stack size for - new threads. Thread stacks (including the main thread's - stack) live on the heap, and grow as required. The default - value is good for concurrent applications with lots of small - threads; if your program doesn't fit this model then - increasing this option may help performance. - - The main thread is normally started with a slightly - larger heap to cut down on unnecessary stack growth while - the program is starting up. - + + [Default: 1k] Set the initial stack size for new + threads. (Note: this flag used to be + simply , but was renamed + to in GHC 7.2.1. The old name is + still accepted for backwards compatibility, but that may + be removed in a future version). + + + + Thread stacks (including the main thread's stack) live on + the heap. As the stack grows, new stack chunks are added + as required; if the stack shrinks again, these extra stack + chunks are reclaimed by the garbage collector. The + default initial stack size is deliberately small, in order + to keep the time and space overhead for thread creation to + a minimum, and to make it practical to spawn threads for + even tiny pieces of work. + + + + + + + size + RTS + option + stackchunk size + + + + [Default: 32k] Set the size of “stack + chunks”. When a thread's current stack overflows, a + new stack chunk is created and added to the thread's + stack, until the limit set by is + reached. + + + + The advantage of smaller stack chunks is that the garbage + collector can avoid traversing stack chunks if they are + known to be unmodified since the last collection, so + reducing the chunk size means that the garbage collector + can identify more stack as unmodified, and the GC overhead + might be reduced. On the other hand, making stack chunks + too small adds some overhead as there will be more + overflow/underflow between chunks. The default setting of + 32k appears to be a reasonable compromise in most cases. + + + + + + + size + RTS + option + stackchunk buffer size + + + + [Default: 1k] Sets the stack chunk buffer size. + When a stack chunk overflows and a new stack chunk is + created, some of the data from the previous stack chunk is + moved into the new chunk, to avoid an immediate underflow + and repeated overflow/underflow at the boundary. The + amount of stack moved is set by the + option. + + + Note that to avoid wasting space, this value should + typically be less than 10% of the size of a stack + chunk (), because in a chain of stack + chunks, each chunk will have a gap of unused space of this + size. + + @@ -440,9 +518,14 @@ [Default: 8M] Set the maximum stack size for an individual thread to size - bytes. This option is there purely to stop the program - eating up all the available memory in the machine if it gets - into an infinite loop. + bytes. If the thread attempts to exceed this limit, it will + be send the StackOverflow exception. + + + This option is there mainly to stop the program eating up + all the available memory in the machine if it gets into an + infinite loop. + @@ -850,15 +933,16 @@ - + RTS option Log events in binary format to the file program.eventlog, - where type indicates the type - of events to log. Currently there is only one type + where flags is a sequence of + zero or more characters indicating which kinds of events + to log. Currently there is only one type supported: -ls, for scheduler events. @@ -878,13 +962,19 @@ - + flags RTS option Log events as text to standard output, instead of to the .eventlog file. + The flags are the same as + for , with the additional + option t which indicates that the + each event printed should be preceded by a timestamp value + (in the binary .eventlog file, all + events are automatically associated with a timestamp). @@ -973,20 +1063,13 @@ Produce “ticky-ticky” statistics at the - end of the program run. The file - business works just like on the RTS - option (above). - - “Ticky-ticky” statistics are counts of - various program actions (updates, enters, etc.) The program - must have been compiled using - - (a.k.a. “ticky-ticky profiling”), and, for it to - be really useful, linked with suitable system libraries. - Not a trivial undertaking: consult the installation guide on - how to set things up for easy “ticky-ticky” - profiling. For more information, see . + end of the program run (only available if the program was + linked with ). + The file business works just like + on the RTS option, above. + + For more information on ticky-ticky profiling, see + . @@ -1045,6 +1128,20 @@ + + Linker flags to change RTS behaviour + + RTS behaviour, changing + + + GHC lets you exercise rudimentary control over the RTS settings + for any given program, by using the -with-rtsopts + linker flag. For example, to set -H128m -K1m, + link with -with-rtsopts="-H128m -K1m". + + + + “Hooks” to change RTS behaviour @@ -1064,7 +1161,8 @@ The hook ghc_rts_optsghc_rts_opts lets you set RTS - options permanently for a given program. A common use for this is + options permanently for a given program, in the same way as the + newer linker option does. A common use for this is to give your program a default heap and/or stack size that is greater than the default. For example, to set -H128m -K1m, place the following definition in a C source @@ -1270,7 +1368,6 @@ $ ./a.out +RTS --info