Changes between Initial Version and Version 1 of FastMalloc Glossary

Timestamp:

Mar 26, 2010, 10:37:17 AM (16 years ago)

Author:

ggaren@apple.com

Comment:

--

FastMalloc Glossary

@@ +1 @@
+Here is a glossary of terms used in FastMalloc. Sometimes, more than one term is used for the same thing.
+
+'''sizeclass | class'''
+{{{
+number from [1, kNumClasses] identifying a size grouping
+0 sizeclass means large allocation
+objects of the same sizeclass:
+    have the same true allocation size
+    are in the same free list
+}}}
+
+'''classindex'''
+{{{
+location of 'size' in the sizeclass array
+classindex values are cached to avoid repeat math
+}}}
+
+
+'''span | descriptor'''
+{{{
+metadata for a contiguous run of pages
+either a single large allocation or
+parceled into bytesize(sizeclass) units
+maintains a free list for those units
+maintains a total reference count for those units
+}}}
+
+
+'''pagemap'''
+{{{
+[pageID => span] mapping for all pageIDs in the address space
+more than one pageID can map to the same span
+}}}
+
+
+'''page'''
+{{{
+kPageSize chunk of memory
+}}}
+
+
+'''pageID'''
+{{{
+number from [0, kNumPages] identifying a page
+pageID * kPageSize = address of page
+}}}
+
+'''object'''
+{{{
+item in a free list
+}}}
+
+'''split (verb)'''
+{{{
+break a span into two parts (used by memalign)
+}}}
+
+'''carve (verb)'''
+{{{
+allocate a span, possibly splitting it (used by pageheap allocation functions)
+}}}
+
+'''pageheap'''
+{{{
+central span and page allocator
+requires locking
+maintains the pagemap
+keeps free spanlists for spans
+}}}
+
+'''spanlist'''
+{{{
+2 linked lists of spans:
+    mmaped (vm live)
+    madvised (vm dead)
+}}}
+
+'''threadcache | heap | threadheap'''
+{{{
+per-thread free lists for various size classes
+}}}
+
+'''central_cache'''
+{{{
+central list for size classes
+one lock per list
+all normal-sized allocation originates in the central_cache (but may be cached in a threadcache)
+}}}
+