diff options
Diffstat (limited to 'libc/stdlib/malloc')
| -rw-r--r-- | libc/stdlib/malloc/Makefile | 2 | ||||
| -rw-r--r-- | libc/stdlib/malloc/free.c | 113 | ||||
| -rw-r--r-- | libc/stdlib/malloc/heap.h | 70 | ||||
| -rw-r--r-- | libc/stdlib/malloc/heap_append_free.c | 71 | ||||
| -rw-r--r-- | libc/stdlib/malloc/heap_free.c | 6 | ||||
| -rw-r--r-- | libc/stdlib/malloc/malloc.c | 110 | ||||
| -rw-r--r-- | libc/stdlib/malloc/malloc.h | 35 | ||||
| -rw-r--r-- | libc/stdlib/malloc/realloc.c | 17 |
8 files changed, 234 insertions, 190 deletions
diff --git a/libc/stdlib/malloc/Makefile b/libc/stdlib/malloc/Makefile index 710f70297..6d1e89186 100644 --- a/libc/stdlib/malloc/Makefile +++ b/libc/stdlib/malloc/Makefile @@ -25,7 +25,7 @@ TOPDIR=../../../ include $(TOPDIR)Rules.mak CSRC = malloc.o free.o realloc.o calloc.o heap_alloc.o \ - heap_alloc_at.o heap_free.o heap_append_free.o + heap_alloc_at.o heap_free.o COBJS=$(patsubst %.c,%.o, $(CSRC)) OBJS=$(COBJS) diff --git a/libc/stdlib/malloc/free.c b/libc/stdlib/malloc/free.c index 4721d0269..41deed737 100644 --- a/libc/stdlib/malloc/free.c +++ b/libc/stdlib/malloc/free.c @@ -12,24 +12,119 @@ */ #include <stdlib.h> +#include <unistd.h> #include <sys/mman.h> #include "malloc.h" #include "heap.h" +/* Try to release the free-area FA in HEAP back to the system. */ +static void +unmap_free_area (struct heap *heap, struct heap_free_area *fa) +{ + unsigned long start, end; +#ifndef MALLOC_USE_SBRK + unsigned long unmap_start, unmap_end; +#endif + + end = (unsigned long)HEAP_FREE_AREA_END (fa); + +#ifdef MALLOC_USE_SBRK + /* When using sbrk, we only shrink the heap from the end. It would be + possible to allow _both_ -- shrinking via sbrk when possible, and + otherwise shrinking via munmap, but this results in holes in memory + that prevent the brk from every growing back down; since we only ever + grow the heap via sbrk, this tends to produce a continuously growing + brk (though the actual memory is unmapped), which could eventually run + out of address space. Note that `sbrk(0)' shouldn't normally do a + system call, so this test is reasonably cheap. */ + if ((void *)end != sbrk (0)) + { + MALLOC_DEBUG (" not unmapping: 0x%lx - 0x%lx (%d bytes)\n", + (unsigned long)HEAP_FREE_AREA_START (fa), + (unsigned long)HEAP_FREE_AREA_END (fa), + fa->size); + return; + } +#endif + + start = (unsigned long)HEAP_FREE_AREA_START (fa); + + MALLOC_DEBUG (" unmapping: 0x%lx - 0x%lx (%ld bytes)\n", + start, end, end - start); + + /* Remove FA from the heap. */ + __heap_unlink_free_area (heap, fa); + + if (!fa->next && !fa->prev) + /* We want to avoid the heap from losing all memory, so reserve a bit. + This test is only a heuristic -- the existance of another free area, + even if it's smaller than MALLOC_MIN_SIZE, will cause us not to + reserve anything. */ + { + /* Put the reserved memory back in the heap; we asssume that + MALLOC_UNMAP_THRESHOLD is greater than MALLOC_MIN_SIZE, so we use + the latter unconditionally here. */ + __heap_free (heap, (void *)start, MALLOC_MIN_SIZE); + start += MALLOC_MIN_SIZE; + } + +#ifdef MALLOC_USE_SBRK + + sbrk (start - end); + +#else /* !MALLOC_USE_SBRK */ + + /* MEM/LEN may not be page-aligned, so we have to page-align them, and + return any left-over bits on the end to the heap. */ + unmap_start = MALLOC_ROUND_UP_TO_PAGE_SIZE (start); + unmap_end = MALLOC_ROUND_DOWN_TO_PAGE_SIZE (end); + + /* We have to be careful that any left-over bits are large enough to + return. Note that we _don't check_ to make sure there's room to + grow/shrink the start/end by another page, we just assume that the + unmap threshold is high enough so that this is always safe (i.e., it + should probably be at least 3 pages). */ + if (unmap_start > start) + { + if (unmap_start - start < HEAP_MIN_FREE_AREA_SIZE) + unmap_start += MALLOC_PAGE_SIZE; + __heap_free (heap, (void *)start, unmap_start - start); + } + if (end > unmap_end) + { + if (end - unmap_end < HEAP_MIN_FREE_AREA_SIZE) + unmap_end -= MALLOC_PAGE_SIZE; + __heap_free (heap, (void *)unmap_end, end - unmap_end); + } + + if (unmap_end > unmap_start) + munmap ((void *)unmap_start, unmap_end - unmap_start); + +#endif /* MALLOC_USE_SBRK */ +} + + void free (void *mem) { - size_t size; + if (mem) + { + size_t size; + struct heap_free_area *fa; + + mem -= MALLOC_ALIGNMENT; + size = *(size_t *)mem; - mem = (size_t *)mem - 1; - size = *(size_t *)mem; + MALLOC_DEBUG ("free: 0x%lx (base = 0x%lx, total_size = %d)\n", + (long)mem + MALLOC_ALIGNMENT, (long)mem, size); - MALLOC_DEBUG ("free: 0x%lx (base = 0x%lx, total_size = %d)\n", - (long)mem + sizeof (size_t), (long)mem, size); + fa = __heap_free (&__malloc_heap, mem, size); - if (size >= MALLOC_MMAP_THRESHOLD) - munmap (mem, size); - else - __heap_free (&__malloc_heap, mem, size); + /* Now we check to see if FA has grown big enough that it should be + unmapped. */ + if (HEAP_FREE_AREA_SIZE (fa) >= MALLOC_UNMAP_THRESHOLD) + /* Get rid of it. */ + unmap_free_area (&__malloc_heap, fa); + } } diff --git a/libc/stdlib/malloc/heap.h b/libc/stdlib/malloc/heap.h index 0d6465050..589bf42b0 100644 --- a/libc/stdlib/malloc/heap.h +++ b/libc/stdlib/malloc/heap.h @@ -29,10 +29,9 @@ typedef int heap_mutex_t; #endif - -/* The unit in which allocation is done, due to alignment constraints, etc. - All allocation requests are rounded up to a multiple of this size. - Must be a power of 2. */ +/* The heap allocates in multiples of, and aligned to, HEAP_GRANULARITY. + HEAP_GRANULARITY must be a power of 2. Malloc depends on this being the + same as MALLOC_ALIGNMENT. */ #define HEAP_GRANULARITY (sizeof (double)) @@ -40,10 +39,11 @@ typedef int heap_mutex_t; of memory can be allocated. */ struct heap { + /* A list of memory in the heap available for allocation. */ struct heap_free_area *free_areas; + heap_mutex_t lock; }; - #define HEAP_INIT { 0, HEAP_MUTEX_INIT } @@ -61,6 +61,8 @@ struct heap_free_area /* Return the address of the beginning of the frea area FA. FA is evaulated multiple times. */ #define HEAP_FREE_AREA_START(fa) ((void *)((char *)(fa + 1) - (fa)->size)) +/* Return the size of the frea area FA. */ +#define HEAP_FREE_AREA_SIZE(fa) ((fa)->size) /* Rounds SZ up to be a multiple of HEAP_GRANULARITY. */ @@ -74,6 +76,8 @@ struct heap_free_area (sizeof (struct heap_free_area) + HEAP_ADJUST_SIZE (1)) +/* Change this to `#if 1' to cause the heap routines to emit debugging info + to stderr. */ #if 0 #include <stdio.h> static void HEAP_DEBUG (struct heap *heap, const char *str) @@ -81,18 +85,24 @@ static void HEAP_DEBUG (struct heap *heap, const char *str) static int recursed = 0; if (! recursed) { - struct heap_free_area *fa; + struct heap_free_area *fa, *prev; recursed = 1; fprintf (stderr, " %s: heap @0x%lx:\n", str, (long)heap); - for (fa = heap->free_areas; fa; fa = fa->next) - fprintf (stderr, - " 0x%lx: 0x%lx - 0x%lx (%d)\tN=0x%lx, P=0x%lx\n", - (long)fa, - (long)HEAP_FREE_AREA_START (fa), - (long)HEAP_FREE_AREA_END (fa), - fa->size, - (long)fa->prev, - (long)fa->next); + for (prev = 0, fa = heap->free_areas; fa; prev = fa, fa = fa->next) + { + fprintf (stderr, + " 0x%lx: 0x%lx - 0x%lx (%d)\tP=0x%lx, N=0x%lx\n", + (long)fa, + (long)HEAP_FREE_AREA_START (fa), + (long)HEAP_FREE_AREA_END (fa), + fa->size, + (long)fa->prev, + (long)fa->next); + if (fa->prev != prev) + fprintf (stderr, + " PREV POINTER CORRUPTED!!!! P=0x%lx should be 0x%lx\n", + (long)fa->prev, (long)prev); + } recursed = 0; } } @@ -101,6 +111,18 @@ static void HEAP_DEBUG (struct heap *heap, const char *str) #endif +/* Remove the free-area FA from HEAP. */ +extern inline void +__heap_unlink_free_area (struct heap *heap, struct heap_free_area *fa) +{ + if (fa->next) + fa->next->prev = fa->prev; + if (fa->prev) + fa->prev->next = fa->next; + else + heap->free_areas = fa->next; +} + /* Allocate SIZE bytes from the front of the free-area FA in HEAP, and return the amount actually allocated (which may be more than SIZE). */ extern inline size_t @@ -113,12 +135,7 @@ __heap_free_area_alloc (struct heap *heap, /* There's not enough room left over in FA after allocating the block, so just use the whole thing, removing it from the list of free areas. */ { - if (fa->next) - fa->next->prev = fa->prev; - if (fa->prev) - fa->prev->next = fa->next; - else - heap->free_areas = fa->next; + __heap_unlink_free_area (heap, fa); /* Remember that we've alloced the whole area. */ size = fa_size; } @@ -139,10 +156,7 @@ extern void *__heap_alloc (struct heap *heap, size_t *size); allocated, or 0 if we failed. */ extern size_t __heap_alloc_at (struct heap *heap, void *mem, size_t size); -/* Return the memory area MEM of size SIZE to HEAP. */ -extern void __heap_free (struct heap *heap, void *mem, size_t size); - -/* If the memory area MEM, of size SIZE, immediately follows an existing - free-area in HEAP, use it to extend that free-area, and return true; - otherwise return false. */ -extern int __heap_append_free (struct heap *heap, void *mem, size_t size); +/* Return the memory area MEM of size SIZE to HEAP. + Returns the heap free area into which the memory was placed. */ +extern struct heap_free_area *__heap_free (struct heap *heap, + void *mem, size_t size); diff --git a/libc/stdlib/malloc/heap_append_free.c b/libc/stdlib/malloc/heap_append_free.c deleted file mode 100644 index d67f46495..000000000 --- a/libc/stdlib/malloc/heap_append_free.c +++ /dev/null @@ -1,71 +0,0 @@ -/* - * libc/stdlib/malloc/heap_append_free.c -- append memory to a heap free area - * - * Copyright (C) 2002 NEC Corporation - * Copyright (C) 2002 Miles Bader <miles@gnu.org> - * - * This file is subject to the terms and conditions of the GNU Lesser - * General Public License. See the file COPYING.LIB in the main - * directory of this archive for more details. - * - * Written by Miles Bader <miles@gnu.org> - */ - -#include <stdlib.h> - -#include "heap.h" - - -/* If the block MEM, of size SIZE, immediately follows an existing free-area - in HEAP, use it to extend that free-area, and return true; otherwise return - false. */ -int -__heap_append_free (struct heap *heap, void *mem, size_t size) -{ - int success = 0; - struct heap_free_area *fa; - - __heap_lock (heap); - - HEAP_DEBUG (heap, "before __heap_append_free"); - - /* Find an adjacent free-list entry. */ - for (fa = heap->free_areas; fa; fa = fa->next) - if (HEAP_FREE_AREA_END (fa) == mem) - /* MEM follows FA, extend FA to include it. Since the descriptor for FA - is located at the end, we must actually write a new descriptor. Note - that we _don't_ handle the case where the extended FA can be merged - with a following free area; this is because this function is - generally only used in cases were we believe that usually won't - happen (it doesn't cause any incorrectness, and the two blocks can be - merged by __heap_free later). */ - { - struct heap_free_area *next_fa = fa->next; - struct heap_free_area *prev_fa = fa->prev; - size_t fa_size = fa->size; - struct heap_free_area *new_fa = - (struct heap_free_area *)((char *)fa + size); - - /* Update surrounding free-areas to point to FA's new address. */ - if (prev_fa) - prev_fa->next = new_fa; - else - heap->free_areas = new_fa; - if (next_fa) - next_fa->prev = new_fa; - - /* Fill in the moved descriptor. */ - new_fa->prev = prev_fa; - new_fa->next = next_fa; - new_fa->size = fa_size + size; - - success = 1; - break; - } - - HEAP_DEBUG (heap, "after __heap_append_free"); - - __heap_unlock (heap); - - return success; -} diff --git a/libc/stdlib/malloc/heap_free.c b/libc/stdlib/malloc/heap_free.c index d8eaf7e66..ac7e00be3 100644 --- a/libc/stdlib/malloc/heap_free.c +++ b/libc/stdlib/malloc/heap_free.c @@ -17,7 +17,7 @@ /* Return the memory area MEM of size SIZE to HEAP. */ -void +struct heap_free_area * __heap_free (struct heap *heap, void *mem, size_t size) { struct heap_free_area *prev_fa, *fa, *new_fa; @@ -120,8 +120,12 @@ __heap_free (struct heap *heap, void *mem, size_t size) if (fa) fa->prev = new_fa; + fa = new_fa; + done: HEAP_DEBUG (heap, "after __heap_free"); __heap_unlock (heap); + + return fa; } diff --git a/libc/stdlib/malloc/malloc.c b/libc/stdlib/malloc/malloc.c index 32d56c153..0e84bf646 100644 --- a/libc/stdlib/malloc/malloc.c +++ b/libc/stdlib/malloc/malloc.c @@ -12,25 +12,14 @@ */ #include <stdlib.h> +#include <unistd.h> #include <sys/mman.h> #include "malloc.h" #include "heap.h" -/* When we give memory to the heap, start this many bytes after the - beginning of the mmaped block. This is because we must ensure that - malloc return values are aligned to MALLOC_ALIGNMENT, but since we need - to use one word _before_ the beginning of that, we actually want the heap - to return values that are MALLOC_ALIGNMENT aligned - sizeof (size_t). - Since the heap always allocates in multiples of HEAP_GRANULARITY, we can - do this by (1) ensuring that HEAP_GRANULARITY is a multiple of - MALLOC_ALIGNMENT, and (2) making sure that the heap's free areas start - sizeof(size_t) bytes before our required alignment. */ -#define MALLOC_HEAP_BLOCK_SHIM (MALLOC_ALIGNMENT - sizeof (size_t)) - - -/* The heap used for small allocations. */ +/* The malloc heap. */ struct heap __malloc_heap = HEAP_INIT; @@ -40,56 +29,57 @@ void *malloc (size_t size) MALLOC_DEBUG ("malloc: %d bytes\n", size); - /* Include an extra word to record the size of the allocated block. */ - size += sizeof (size_t); - - if (size >= MALLOC_MMAP_THRESHOLD) - /* Use mmap for large allocations. */ - { - /* Make sure we request enough memory to align the result correctly, - and that SIZE reflects that mmap hands back whole pages. */ - size += MALLOC_ROUND_UP_TO_PAGE_SIZE (MALLOC_ALIGNMENT - sizeof(size_t)); + /* Include extra space to record the size of the allocated block. */ + size += MALLOC_ROUND_UP (sizeof (size_t), MALLOC_ALIGNMENT); - mem = mmap (0, size, PROT_READ | PROT_WRITE, - MAP_SHARED | MAP_ANONYMOUS, 0, 0); - if (mem == MAP_FAILED) - return 0; - } - else - /* Use the heap for small allocations. */ + mem = __heap_alloc (&__malloc_heap, &size); + if (! mem) + /* We couldn't allocate from the heap, so get some more memory + from the system, add it to the heap, and try again. */ { - mem = __heap_alloc (&__malloc_heap, &size); - - if (! mem) - /* We couldn't allocate from the heap, so get some more memory - from the system, add it to the heap, and try again. */ + /* If we're trying to allocate a block bigger than the default + MALLOC_HEAP_EXTEND_SIZE, make sure we get enough to hold it. */ + size_t block_size + = (size < MALLOC_HEAP_EXTEND_SIZE + ? MALLOC_HEAP_EXTEND_SIZE + : MALLOC_ROUND_UP_TO_PAGE_SIZE (size)); + /* Allocate the new heap block. */ +#ifdef MALLOC_USE_SBRK + /* Use sbrk we can, as it's faster than mmap, and guarantees + contiguous allocation. */ + void *block = sbrk (block_size); +#else + /* Otherwise, use mmap. */ + void *block = mmap (0, block_size, PROT_READ | PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, 0, 0); +#endif + + if (block != (void *)-1) { - /* If we're trying to allocate a block bigger than the default - MALLOC_HEAP_EXTEND_SIZE, make sure we get enough to hold it. */ - size_t block_size = (size < MALLOC_HEAP_EXTEND_SIZE - ? MALLOC_HEAP_EXTEND_SIZE - : MALLOC_ROUND_UP_TO_PAGE_SIZE (size)); - /* Allocate the new heap block. */ - void *block = mmap (0, block_size, - PROT_READ | PROT_WRITE, - MAP_SHARED | MAP_ANONYMOUS, 0, 0); - - if (block != MAP_FAILED) +#ifdef MALLOC_USE_SBRK + /* Because sbrk can return results of arbitrary + alignment, align the result to a MALLOC_ALIGNMENT boundary. */ + long aligned_block = MALLOC_ROUND_UP ((long)block, MALLOC_ALIGNMENT); + if (block != (void *)aligned_block) + /* Have to adjust. We should only have to actually do this + the first time (after which we will have aligned the brk + correctly). */ { - /* Put BLOCK into the heap. We first try to append BLOCK to - an existing free area, which is more efficient because it - doesn't require using a `shim' at the beginning (which - would prevent merging free-areas); since mmap often returns - contiguous areas, this is worth it. */ - if (! __heap_append_free (&__malloc_heap, block, block_size)) - /* Couldn't append, just add BLOCK as a new free-area. */ - __heap_free (&__malloc_heap, - block + MALLOC_HEAP_BLOCK_SHIM, - block_size - MALLOC_HEAP_BLOCK_SHIM); - - /* Try again to allocate. */ - mem = __heap_alloc (&__malloc_heap, &size); + /* Move the brk to reflect the alignment; our next allocation + should start on exactly the right alignment. */ + sbrk (aligned_block - (long)block); + block = (void *)aligned_block; } +#endif /* MALLOC_USE_SBRK */ + + MALLOC_DEBUG (" adding memory: 0x%lx - 0x%lx (%d bytes)\n", + (long)block, (long)block + block_size, block_size); + + /* Put BLOCK into the heap. */ + __heap_free (&__malloc_heap, block, block_size); + + /* Try again to allocate. */ + mem = __heap_alloc (&__malloc_heap, &size); } } @@ -97,10 +87,10 @@ void *malloc (size_t size) /* Record the size of this block just before the returned address. */ { *(size_t *)mem = size; - mem = (size_t *)mem + 1; + mem += MALLOC_ALIGNMENT; MALLOC_DEBUG (" malloc: returning 0x%lx (base:0x%lx, total_size:%d)\n", - (long)mem, (long)mem - sizeof (size_t), size); + (long)mem, (long)mem - MALLOC_ALIGNMENT, size); } return mem; diff --git a/libc/stdlib/malloc/malloc.h b/libc/stdlib/malloc/malloc.h index 187477a67..0cab1dba2 100644 --- a/libc/stdlib/malloc/malloc.h +++ b/libc/stdlib/malloc/malloc.h @@ -23,11 +23,26 @@ satisfy a particularly big request). */ #define MALLOC_HEAP_EXTEND_SIZE MALLOC_PAGE_SIZE -/* The threshold above which blocks are allocated/freed with mmap/munmap, - rather than using the heap. */ -#define MALLOC_MMAP_THRESHOLD (8*MALLOC_PAGE_SIZE) +/* When a heap free-area grows above this size, try to unmap it, releasing + the memory back to the system. */ +#define MALLOC_UNMAP_THRESHOLD (8*MALLOC_PAGE_SIZE) +/* When unmapping a free-area, retain this many bytes if it's the only one, + to avoid completely emptying the heap. This is only a heuristic -- the + existance of another free area, even if it's smaller than + MALLOC_MIN_SIZE, will cause us not to reserve anything. */ +#define MALLOC_MIN_SIZE (2*MALLOC_PAGE_SIZE) +/* For systems with an MMU, use sbrk to map/unmap memory for the malloc + heap, instead of mmap/munmap. This is a tradeoff -- sbrk is faster than + mmap/munmap, and guarantees contiguous allocation, but is also less + flexible, and causes the heap to only be shrinkable from the end. */ +#ifdef __UCLIBC_HAS_MMU__ +#define MALLOC_USE_SBRK +#endif + + +/* Change this to `#if 1' to cause malloc to emit debugging info to stderr. */ #if 0 #include <stdio.h> #define MALLOC_DEBUG(fmt, args...) fprintf (stderr, fmt , ##args) @@ -36,10 +51,20 @@ #endif +/* Return SZ rounded down to POWER_OF_2_SIZE (which must be power of 2). */ +#define MALLOC_ROUND_DOWN(sz, power_of_2_size) \ + ((sz) & ~(power_of_2_size - 1)) +/* Return SZ rounded to POWER_OF_2_SIZE (which must be power of 2). */ +#define MALLOC_ROUND_UP(sz, power_of_2_size) \ + MALLOC_ROUND_DOWN ((sz) + (power_of_2_size - 1), (power_of_2_size)) + +/* Return SZ rounded down to a multiple MALLOC_PAGE_SIZE. */ +#define MALLOC_ROUND_DOWN_TO_PAGE_SIZE(sz) \ + MALLOC_ROUND_DOWN (sz, MALLOC_PAGE_SIZE) /* Return SZ rounded up to a multiple MALLOC_PAGE_SIZE. */ #define MALLOC_ROUND_UP_TO_PAGE_SIZE(sz) \ - (((sz) + (MALLOC_PAGE_SIZE - 1)) & ~(MALLOC_PAGE_SIZE - 1)) + MALLOC_ROUND_UP (sz, MALLOC_PAGE_SIZE) -/* The heap used for small allocations. */ +/* The malloc heap. */ extern struct heap __malloc_heap; diff --git a/libc/stdlib/malloc/realloc.c b/libc/stdlib/malloc/realloc.c index f18ed9eb6..091b3392b 100644 --- a/libc/stdlib/malloc/realloc.c +++ b/libc/stdlib/malloc/realloc.c @@ -25,7 +25,7 @@ void *realloc (void *mem, size_t new_size) return malloc (new_size); else { - void *base_mem = (size_t *)mem - 1; + void *base_mem = mem - MALLOC_ALIGNMENT; size_t size = *(size_t *)base_mem; MALLOC_DEBUG ("realloc: 0x%lx, %d (base = 0x%lx, total_size = %d)\n", @@ -39,20 +39,7 @@ void *realloc (void *mem, size_t new_size) size_t ext_size = new_size - size; void *ext_addr = (char *)base_mem + ext_size; - if (size >= MALLOC_MMAP_THRESHOLD) - /* Try to extend this block in place using mmap. */ - { - ext_size += MALLOC_ROUND_UP_TO_PAGE_SIZE (ext_size); - - new_mem = mmap (ext_addr, ext_size, PROT_READ | PROT_WRITE, - MAP_FIXED | MAP_SHARED | MAP_ANONYMOUS, 0, 0); - if (new_mem == MAP_FAILED) - /* Can't do it. */ - ext_size = 0; - } - else - ext_size = __heap_alloc_at (&__malloc_heap, ext_addr, ext_size); - + ext_size = __heap_alloc_at (&__malloc_heap, ext_addr, ext_size); if (! ext_size) /* Our attempts to extend MEM in place failed, just allocate-and-copy. */ |