Commit da407089 authored by simonm's avatar simonm

[project @ 1999-02-02 15:30:45 by simonm]

Update new RTS options for the garbage collector.
parent 8a9a56e2
......@@ -41,4 +41,16 @@ occur in the source code.
<item> Two new functions exported from <tt/ST/ (and <tt/LazyST/):
<tt/unsafeIOToST/ and <tt/stToIO/.
<item> The <tt/+RTS -H&lt;size&gt;/ option is reinstated. Now it
means "use about this much memory" (see Section <ref
id="rts-options-gc" name="RTS options to control the garbage
collector">). This option was added mainly so that 4.02 GC times look
good compared to 3.02 :-).
<item> <tt/finalise/ and <tt/mkWeakNoFinaliser/ operations added to
<tt/Weak/ library.
<item> Ticky-ticky profiling works again (cost-centre profiling is
still broken).
</itemize>
......@@ -63,6 +63,42 @@ operation, but there are several things that can be tweaked for
maximum performance.
<descrip>
<tag>@-A<size>@:</tag>
<nidx>-A&lt;size&gt; RTS option</nidx>
<nidx>allocation area, size</nidx>
[Default: 256k] Set the allocation area size used by the garbage
collector. The allocation area (actually generation 0 step 0) is
fixed and is never resized (unless you use <tt/-H/, below).
Increasing the allocation area size may or may not give better
performance (a bigger allocation area means worse cache behaviour but
fewer garbage collections and less promotion).
With only 1 generation (<tt/-G1/) the <tt/-A/ option specifies the
minimum allocation area, since the actual size of the allocation area
will be resized according to the amount of data in the heap (see
<tt/-F/, below).
<tag>@-F<factor>@:</tag>
<nidx>-F&lt;factor&gt; RTS option</nidx>
<nidx>heap size, factor</nidx>
[Default: 2] This option controls the amount of memory reserved for
the older generations (and in the case of a two space collector the
size of the allocation area) as a factor of the amount of live data.
For example, if there was 2M of live data in the oldest generation
when we last collected it, then by default we'll wait until it grows
to 4M before collecting it again.
The default seems to work well here. If you have plenty of memory, it
is usually better to use <tt/-H&lt;size&gt;/ than to increase
<tt/-F&lt;factor&gt;/.
The <tt/-F/ setting will be automatically reduced by the garbage
collector when the maximum heap size (the <tt/-M&lt;size&gt;/ setting)
is approaching.
<tag>@-G<generations>@:</tag>
<nidx>-G&lt;generations&gt; RTS option</nidx>
<nidx>generations, number of</nidx>
......@@ -76,22 +112,25 @@ collected.
Specifying 1 generation with @+RTS -G1@ gives you a simple 2-space
collector, as you would expect. In a 2-space collector, the @-A@
option (see below) specifies the <em/minimum/ allocation area size,
option (see above) specifies the <em/minimum/ allocation area size,
since the allocation area will grow with the amount of live data in
the heap. In a multi-generational collector the allocation area is a
fixed size.
<tag>@-A<size>@:</tag>
<nidx>-A&lt;size&gt; RTS option</nidx>
<nidx>allocation area, size</nidx>
[Default: 256k] Set the allocation area size used by the garbage
collector. The allocation area (actually generation 0 step 0) is
fixed and is never resized.
Increasing the allocation area size may or may not give better
performance (a bigger allocation area means worse cache behaviour but
fewer garbage collections and less promotion).
fixed size (unless you use the <tt/-H/ option, see below).
<tag>@-H<size>@:</tag>
<nidx>-H&lt;size&gt; RTS option</nidx>
<nidx>heap size, suggested</nidx>
[Default: 0] This option provides a "suggested heap size" for the
garbage collector. The garbage collector will use about this much
memory until the program residency grows and the heap size needs to be
expanded to retain reasonable performance.
By default, the heap will start small, and grow and shrink as
necessary. This can be bad for performance, so if you have plenty of
memory it's worthwhile supplying a big <tt/-H&lt;size&gt/. For
improving GC performance, using <tt/-H&lt;size&gt/ is usually a better
bet than <tt/-A&lt;size&gt/.
<tag>@-k<size>@:</tag>
<nidx>-k&lt;size&gt; RTS option</nidx>
......
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