From da407089c1b488c9cd2804494b99a416747b2a59 Mon Sep 17 00:00:00 2001 From: simonm <unknown> Date: Tue, 2 Feb 1999 15:30:46 +0000 Subject: [PATCH] [project @ 1999-02-02 15:30:45 by simonm] Update new RTS options for the garbage collector. --- ghc/docs/users_guide/4-02-notes.vsgml | 12 ++++ ghc/docs/users_guide/runtime_control.vsgml | 67 +++++++++++++++++----- 2 files changed, 65 insertions(+), 14 deletions(-) diff --git a/ghc/docs/users_guide/4-02-notes.vsgml b/ghc/docs/users_guide/4-02-notes.vsgml index 918079558a00..b162e496447d 100644 --- a/ghc/docs/users_guide/4-02-notes.vsgml +++ b/ghc/docs/users_guide/4-02-notes.vsgml @@ -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<size>/ 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> diff --git a/ghc/docs/users_guide/runtime_control.vsgml b/ghc/docs/users_guide/runtime_control.vsgml index eb1da49a073b..19d03c651742 100644 --- a/ghc/docs/users_guide/runtime_control.vsgml +++ b/ghc/docs/users_guide/runtime_control.vsgml @@ -63,6 +63,42 @@ operation, but there are several things that can be tweaked for maximum performance. <descrip> +<tag>@-A<size>@:</tag> +<nidx>-A<size> 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<factor> 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<size>/ than to increase +<tt/-F<factor>/. + +The <tt/-F/ setting will be automatically reduced by the garbage +collector when the maximum heap size (the <tt/-M<size>/ setting) +is approaching. + <tag>@-G<generations>@:</tag> <nidx>-G<generations> 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<size> 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<size> 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<size>/. For +improving GC performance, using <tt/-H<size>/ is usually a better +bet than <tt/-A<size>/. <tag>@-k<size>@:</tag> <nidx>-k<size> RTS option</nidx> -- GitLab