Author: Laurence Tratt <lau...@tratt.net>
Branch:
Changeset: r74939:7ff0e531c521
Date: 2014-12-15 15:35 +0000
http://bitbucket.org/pypy/pypy/changeset/7ff0e531c521/
Log: (arigo, ltratt) Avoid allocating memory when ordereddicts have spare
capacity.
Previously, dicts could yo-yo in size if someone continually added
and removed elements, but the total number of live elements remained
more-or-less constant. This patch changes things so that compaction
of entries happens more often than shrinking of memory. Put another
way, we only shrink the size allocated to an ordereddict when it is
extremely sparsely populated. This reduces GC pressure quite a bit.
diff --git a/rpython/rtyper/lltypesystem/rordereddict.py
b/rpython/rtyper/lltypesystem/rordereddict.py
--- a/rpython/rtyper/lltypesystem/rordereddict.py
+++ b/rpython/rtyper/lltypesystem/rordereddict.py
@@ -575,7 +575,11 @@
@jit.dont_look_inside
def ll_dict_grow(d):
- if d.num_items < d.num_used_items // 4:
+ if d.num_items < d.num_used_items // 2:
+ # At least 50% of the allocated entries are dead, so perform a
+ # compaction. If ll_dict_remove_deleted_items detects that over
+ # 75% of allocated entries are dead, then it will also shrink the
+ # memory allocated at the same time as doing a compaction.
ll_dict_remove_deleted_items(d)
return True
@@ -594,8 +598,10 @@
return False
def ll_dict_remove_deleted_items(d):
- new_allocated = _overallocate_entries_len(d.num_items)
- if new_allocated < len(d.entries) // 2:
+ if d.num_items < len(d.entries) // 4:
+ # At least 75% of the allocated entries are dead, so shrink the memory
+ # allocated as well as doing a compaction.
+ new_allocated = _overallocate_entries_len(d.num_items)
newitems = lltype.malloc(lltype.typeOf(d).TO.entries.TO, new_allocated)
else:
newitems = d.entries
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