/* * 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. */ # ifdefined(__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 */
/* 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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