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* Copyright (c) 1999-2005 Hewlett-Packard Development Company, L.P.
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* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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* Permission is hereby granted to use or copy this program
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* for any purpose, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is granted,
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* provided the above notices are retained, and a notice that the code was
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* modified is included with the above copyright notice.
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* Constants and data structures for "tiny" free lists.
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* These are used for thread-local allocation or in-lined allocators.
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* Each global free list also essentially starts with one of these.
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* However, global free lists are known to the GC. "Tiny" free lists
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* are basically private to the client. Their contents are viewed as
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* "in use" and marked accordingly by the core of the GC.
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* Note that inlined code might know about the layout of these and the constants
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* involved. Thus any change here may invalidate clients, and such changes should
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* be avoided. Hence we keep this as simple as possible.
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* We always set GRANULE_BYTES to twice the length of a pointer.
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* This means that all allocation requests are rounded up to the next
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* multiple of 16 on 64-bit architectures or 8 on 32-bit architectures.
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* This appears to be a reasonable compromise between fragmentation overhead
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* and space usage for mark bits (usually mark bytes).
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* On many 64-bit architectures some memory references require 16-byte
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* alignment, making this necessary anyway.
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* For a few 32-bit architecture (e.g. x86), we may also need 16-byte alignment
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* for certain memory references. But currently that does not seem to be the
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* default for all conventional malloc implementations, so we ignore that
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* It would always be safe, and often useful, to be able to allocate very
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* small objects with smaller alignment. But that would cost us mark bit
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* space, so we no longer do so.
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#ifndef GC_GRANULE_BYTES
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/* GC_GRANULE_BYTES should not be overridden in any instances of the GC */
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/* library that may be shared between applications, since it affects */
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/* the binary interface to the library. */
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# if defined(__LP64__) || defined (_LP64) || defined(_WIN64) \
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|| defined(__s390x__) || defined(__x86_64__) \
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|| defined(__alpha__) || defined(__powerpc64__) \
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|| defined(__arch64__)
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# define GC_GRANULE_BYTES 16
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# define GC_GRANULE_WORDS 2
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# define GC_GRANULE_BYTES 8
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# define GC_GRANULE_WORDS 2
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#endif /* !GC_GRANULE_BYTES */
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#if GC_GRANULE_WORDS == 2
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# define GC_WORDS_TO_GRANULES(n) ((n)>>1)
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# define GC_WORDS_TO_GRANULES(n) ((n)*sizeof(void *)/GRANULE_BYTES)
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/* A "tiny" free list header contains TINY_FREELISTS pointers to */
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/* singly linked lists of objects of different sizes, the ith one */
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/* containing objects i granules in size. Note that there is a list */
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/* of size zero objects. */
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#ifndef GC_TINY_FREELISTS
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# if GC_GRANULE_BYTES == 16
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# define GC_TINY_FREELISTS 25
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# define GC_TINY_FREELISTS 33 /* Up to and including 256 bytes */
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#endif /* !GC_TINY_FREELISTS */
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/* The ith free list corresponds to size i*GRANULE_BYTES */
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/* Internally to the collector, the index can be computed with */
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/* ROUNDED_UP_GRANULES. Externally, we don't know whether */
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/* DONT_ADD_BYTE_AT_END is set, but the client should know. */
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/* Convert a free list index to the actual size of objects */
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/* on that list, including extra space we added. Not an */
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/* inverse of the above. */
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#define RAW_BYTES_FROM_INDEX(i) ((i) * GC_GRANULE_BYTES)
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#endif /* GC_TINY_FL_H */
added
removed
sigscheme/libgcroots/include/gc_tiny_fl.h
