X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fruntime_control.xml;h=22ca59dcd25b1b1f0551bc427d8c00828b69072c;hb=4df9f0ee56ae232e1cf2f9531205af0dd916b496;hp=d35027b73d1d8b54dd139a61b9b43502fbcbfab4;hpb=187b2ab71446eef91b1b5552f6202f3ee8ed2137;p=ghc-hetmet.git
diff --git a/docs/users_guide/runtime_control.xml b/docs/users_guide/runtime_control.xml
index d35027b..22ca59d 100644
--- a/docs/users_guide/runtime_control.xml
+++ b/docs/users_guide/runtime_control.xml
@@ -10,7 +10,7 @@
code and then links it with a non-trivial runtime system (RTS),
which handles storage management, profiling, etc.
- If you use the -rtsopts flag when linking,
+ 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.
@@ -49,8 +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).
@@ -62,14 +62,15 @@
+RTS -M128m -RTS
to the command line.
-
+ Setting global RTS optionsRTS optionsfrom the environmentenvironment variablefor
setting RTS options
- When the -rtsopts flag is used when linking,
+ 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
@@ -424,22 +425,88 @@
- size
+ sizeRTS 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.
+
+
@@ -451,9 +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.
+
@@ -1089,7 +1161,8 @@
The hook ghc_rts_optsghc_rts_optslets 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
@@ -1295,7 +1368,6 @@ $ ./a.out +RTS --info