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Diffstat (limited to 'docs/users_guide/runtime_control.rst')
| -rw-r--r-- | docs/users_guide/runtime_control.rst | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/docs/users_guide/runtime_control.rst b/docs/users_guide/runtime_control.rst index 09e0afd1ae..19135c61ce 100644 --- a/docs/users_guide/runtime_control.rst +++ b/docs/users_guide/runtime_control.rst @@ -285,6 +285,34 @@ performance. allocation area will be resized according to the amount of data in the heap (see :rts-flag:`-F`, below). +.. rts-flag:: -AL ⟨size⟩ + + :default: ``-A`` value + :since: 8.2.1 + + .. index:: + single: allocation area for large objects, size + + Sets the limit on the total size of "large objects" (objects + larger than about 3KB) that can be allocated before a GC is + triggered. By default this limit is the same as the ``-A`` value. + + Large objects are not allocated from the normal allocation area + set by the ``-A`` flag, which is why there is a separate limit for + these. Large objects tend to be much rarer than small objects, so + most programs hit the ``-A`` limit before the ``-AL`` limit. However, + the ``-A`` limit is per-capability, whereas the ``-AL`` limit is global, + so as ``-N`` gets larger it becomes more likely that we hit the + ``-AL`` limit first. To counteract this, it might be necessary to + use a larger ``-AL`` limit when using a large ``-N``. + + To see whether you're making good use of all the memory reseverd + for the allocation area (``-A`` times ``-N``), look at the output of + ``+RTS -S`` and check whether the amount of memory allocated between + GCs is equal to ``-A`` times ``-N``. If not, there are two possible + remedies: use ``-n`` to set a nursery chunk size, or use ``-AL`` to + increase the limit for large objects. + .. rts-flag:: -O ⟨size⟩ :default: 1m |