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86 lines
4.2 KiB
C
86 lines
4.2 KiB
C
/*
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* Copyright (c) 1999-2005 Hewlett-Packard Development Company, L.P.
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*
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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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*
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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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*/
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#ifndef GC_TINY_FL_H
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#define GC_TINY_FL_H
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/* Constants and data structures for "tiny" free lists. These are */
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/* 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 */
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/* constants involved. Thus any change here may invalidate clients, */
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/* and such changes should be avoided. Hence we keep this as simple */
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/* as possible. */
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/* We always set GC_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 */
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/* overhead 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. For a few 32-bit */
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/* architectures (e.g. x86), we may also need 16-byte alignment for */
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/* certain memory references. But currently that does not seem to be */
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/* the default for all conventional malloc implementations, so we */
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/* ignore that problem. */
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/* It would always be safe, and often useful, to be able to allocate */
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/* very small objects with smaller alignment. But that would cost us */
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/* mark bit space, so we no longer do so. */
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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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#ifndef GC_GRANULE_BYTES
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# define GC_GRANULE_WORDS 2
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# if defined(__LP64__) || defined (_LP64) || defined(_WIN64) \
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|| defined(__alpha__) || defined(__arch64__) \
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|| defined(__powerpc64__) || defined(__s390x__) \
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|| (defined(__x86_64__) && !defined(__ILP32__))
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# define GC_GRANULE_BYTES (GC_GRANULE_WORDS * 8 /* sizeof(void*) */)
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# else
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# define GC_GRANULE_BYTES (GC_GRANULE_WORDS * 4 /* sizeof(void*) */)
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# endif
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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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#else
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# define GC_WORDS_TO_GRANULES(n) ((n)*sizeof(void *)/GC_GRANULE_BYTES)
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#endif
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/* A "tiny" free list header contains GC_TINY_FREELISTS pointers to */
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/* singly linked lists of objects of different sizes, the i-th 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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# else
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# define GC_TINY_FREELISTS 33 /* Up to and including 256 bytes */
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# endif
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#endif /* !GC_TINY_FREELISTS */
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/* The i-th free list corresponds to size i*GC_GRANULE_BYTES */
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/* Internally to the collector, the index can be computed with */
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/* ALLOC_REQUEST_GRANS(). 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 GC_RAW_BYTES_FROM_INDEX(i) ((i) * GC_GRANULE_BYTES)
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#endif /* GC_TINY_FL_H */
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