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/*
* Copyright (c) 1999-2005 Hewlett-Packard Development Company, L.P.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
#ifndef GC_TINY_FL_H
#define GC_TINY_FL_H
/*
* Constants and data structures for "tiny" free lists.
* These are used for thread-local allocation or in-lined allocators.
* Each global free list also essentially starts with one of these.
* However, global free lists are known to the GC. "Tiny" free lists
* are basically private to the client. Their contents are viewed as
* "in use" and marked accordingly by the core of the GC.
*
* Note that inlined code might know about the layout of these and the constants
* involved. Thus any change here may invalidate clients, and such changes should
* be avoided. Hence we keep this as simple as possible.
*/
/*
* We always set GC_GRANULE_BYTES to twice the length of a pointer.
* This means that all allocation requests are rounded up to the next
* multiple of 16 on 64-bit architectures or 8 on 32-bit architectures.
* This appears to be a reasonable compromise between fragmentation overhead
* and space usage for mark bits (usually mark bytes).
* On many 64-bit architectures some memory references require 16-byte
* alignment, making this necessary anyway.
* For a few 32-bit architecture (e.g. x86), we may also need 16-byte alignment
* for certain memory references. But currently that does not seem to be the
* default for all conventional malloc implementations, so we ignore that
* problem.
* It would always be safe, and often useful, to be able to allocate very
* small objects with smaller alignment. But that would cost us mark bit
* space, so we no longer do so.
*/
#ifndef GC_GRANULE_BYTES
/* GC_GRANULE_BYTES should not be overridden in any instances of the GC */
/* library that may be shared between applications, since it affects */
/* the binary interface to the library. */
# if defined(__LP64__) || defined (_LP64) || defined(_WIN64) \
|| defined(__s390x__) \
|| (defined(__x86_64__) && !defined(__ILP32__)) \
|| defined(__alpha__) || defined(__powerpc64__) \
|| defined(__arch64__)
# define GC_GRANULE_BYTES 16
# define GC_GRANULE_WORDS 2
# else
# define GC_GRANULE_BYTES 8
# define GC_GRANULE_WORDS 2
# endif
#endif /* !GC_GRANULE_BYTES */
#if GC_GRANULE_WORDS == 2
# define GC_WORDS_TO_GRANULES(n) ((n)>>1)
#else
# define GC_WORDS_TO_GRANULES(n) ((n)*sizeof(void *)/GC_GRANULE_BYTES)
#endif
/* A "tiny" free list header contains TINY_FREELISTS pointers to */
/* singly linked lists of objects of different sizes, the ith one */
/* containing objects i granules in size. Note that there is a list */
/* of size zero objects. */
#ifndef GC_TINY_FREELISTS
# if GC_GRANULE_BYTES == 16
# define GC_TINY_FREELISTS 25
# else
# define GC_TINY_FREELISTS 33 /* Up to and including 256 bytes */
# endif
#endif /* !GC_TINY_FREELISTS */
/* The ith free list corresponds to size i*GC_GRANULE_BYTES */
/* Internally to the collector, the index can be computed with */
/* ROUNDED_UP_GRANULES. Externally, we don't know whether */
/* DONT_ADD_BYTE_AT_END is set, but the client should know. */
/* Convert a free list index to the actual size of objects */
/* on that list, including extra space we added. Not an */
/* inverse of the above. */
#define GC_RAW_BYTES_FROM_INDEX(i) ((i) * GC_GRANULE_BYTES)
#endif /* GC_TINY_FL_H */
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