2 * mempool.c: efficient memory allocation
4 * MonoMemPool is for fast allocation of memory. We free
5 * all memory when the pool is destroyed.
8 * Dietmar Maurer (dietmar@ximian.com)
10 * Copyright 2001-2003 Ximian, Inc (http://www.ximian.com)
11 * Copyright 2004-2009 Novell, Inc (http://www.novell.com)
12 * Copyright 2011 Xamarin Inc. (http://www.xamarin.com)
13 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
21 #include "mempool-internals.h"
24 * MonoMemPool is for fast allocation of memory. We free
25 * all memory when the pool is destroyed.
29 #define ALIGN_SIZE(s) (((s) + MEM_ALIGN - 1) & ~(MEM_ALIGN - 1))
31 // Size of memory at start of mempool reserved for header
32 #define SIZEOF_MEM_POOL (ALIGN_SIZE (sizeof (MonoMemPool)))
35 #define MONO_MEMPOOL_PAGESIZE 4096
36 #define MONO_MEMPOOL_MINSIZE 256
38 #define MONO_MEMPOOL_PAGESIZE 8192
39 #define MONO_MEMPOOL_MINSIZE 512
42 // The --with-malloc-mempools debug-build flag causes mempools to be allocated in single-element blocks, so tools like Valgrind can run better.
43 #if USE_MALLOC_FOR_MEMPOOLS
44 #define INDIVIDUAL_ALLOCATIONS
45 #define MONO_MEMPOOL_PREFER_INDIVIDUAL_ALLOCATION_SIZE 0
47 #define MONO_MEMPOOL_PREFER_INDIVIDUAL_ALLOCATION_SIZE MONO_MEMPOOL_PAGESIZE
51 #define G_LIKELY(a) (a)
52 #define G_UNLIKELY(a) (a)
55 // A mempool is a linked list of memory blocks, each of which begins with this header structure.
56 // The initial block in the linked list is special, and tracks additional information.
58 // Next block after this one in linked list
61 // Size of this memory block only
64 // Used in "initial block" only: Beginning of current free space in mempool (may be in some block other than the first one)
67 // Used in "initial block" only: End of current free space in mempool (ie, the first byte following the end of usable space)
71 // Unused: Imposing floating point memory rules on _MonoMemPool's final field ensures proper alignment of whole header struct
74 // Used in "initial block" only: Number of bytes so far allocated (whether used or not) in the whole mempool
79 static long total_bytes_allocated = 0;
84 * Returns: a new memory pool.
87 mono_mempool_new (void)
89 return mono_mempool_new_size (MONO_MEMPOOL_PAGESIZE);
93 * mono_mempool_new_size:
94 * @initial_size: the amount of memory to initially reserve for the memory pool.
96 * Returns: a new memory pool with a specific initial memory reservation.
99 mono_mempool_new_size (int initial_size)
103 #ifdef INDIVIDUAL_ALLOCATIONS
104 // In individual allocation mode, create initial block with zero storage space.
105 initial_size = SIZEOF_MEM_POOL;
107 if (initial_size < MONO_MEMPOOL_MINSIZE)
108 initial_size = MONO_MEMPOOL_MINSIZE;
111 pool = (MonoMemPool *)g_malloc (initial_size);
114 pool->pos = (guint8*)pool + SIZEOF_MEM_POOL; // Start after header
115 pool->end = (guint8*)pool + initial_size; // End at end of allocated space
116 pool->d.allocated = pool->size = initial_size;
117 total_bytes_allocated += initial_size;
122 * mono_mempool_destroy:
123 * @pool: the memory pool to destroy
125 * Free all memory associated with this pool.
128 mono_mempool_destroy (MonoMemPool *pool)
132 total_bytes_allocated -= pool->d.allocated;
143 * mono_mempool_invalidate:
144 * @pool: the memory pool to invalidate
146 * Fill the memory associated with this pool to 0x2a (42). Useful for debugging.
149 mono_mempool_invalidate (MonoMemPool *pool)
156 memset (p, 42, p->size);
162 * mono_mempool_stats:
163 * @pool: the momory pool we need stats for
165 * Print a few stats about the mempool:
166 * - Total memory allocated (malloced) by mem pool
167 * - Number of chunks/blocks memory is allocated in
168 * - How much memory is available to dispense before a new malloc must occur?
171 mono_mempool_stats (MonoMemPool *pool)
175 guint32 still_free = pool->end - pool->pos;
183 g_print ("Mempool %p stats:\n", pool);
184 g_print ("Total mem allocated: %d\n", pool->d.allocated);
185 g_print ("Num chunks: %d\n", count);
186 g_print ("Free memory: %d\n", still_free);
190 #ifdef TRACE_ALLOCATIONS
191 #include <execinfo.h>
192 #include "metadata/appdomain.h"
193 #include "metadata/metadata-internals.h"
195 static mono_mutex_t mempool_tracing_lock;
196 #define BACKTRACE_DEPTH 7
198 mono_backtrace (int size)
200 void *array[BACKTRACE_DEPTH];
203 static gboolean inited;
206 mono_os_mutex_init_recursive (&mempool_tracing_lock);
210 mono_os_mutex_lock (&mempool_tracing_lock);
211 g_print ("Allocating %d bytes\n", size);
212 symbols = backtrace (array, BACKTRACE_DEPTH);
213 names = backtrace_symbols (array, symbols);
214 for (i = 1; i < symbols; ++i) {
215 g_print ("\t%s\n", names [i]);
218 mono_os_mutex_unlock (&mempool_tracing_lock);
224 * mono_mempool_alloc:
225 * @pool: the memory pool to use
226 * @size: size of the memory entity we are trying to allocate
228 * A mempool is growing; give a recommended size for the next block.
229 * Each block in a mempool should be about 150% bigger than the previous one,
230 * or bigger if it is necessary to include the new entity.
232 * Returns: the recommended size.
235 get_next_size (MonoMemPool *pool, int size)
237 int target = pool->next? pool->next->size: pool->size;
238 size += SIZEOF_MEM_POOL;
239 /* increase the size */
240 target += target / 2;
241 while (target < size) {
242 target += target / 2;
244 if (target > MONO_MEMPOOL_PAGESIZE && size <= MONO_MEMPOOL_PAGESIZE)
245 target = MONO_MEMPOOL_PAGESIZE;
250 * mono_mempool_alloc:
251 * @pool: the memory pool to use
252 * @size: size of the memory block
254 * Allocates a new block of memory in @pool.
256 * Returns: the address of a newly allocated memory block.
259 mono_mempool_alloc (MonoMemPool *pool, guint size)
261 gpointer rval = pool->pos; // Return value
263 // Normal case: Just bump up pos pointer and we are done
264 size = ALIGN_SIZE (size);
265 pool->pos = (guint8*)rval + size;
267 #ifdef TRACE_ALLOCATIONS
268 if (pool == mono_get_corlib ()->mempool) {
269 mono_backtrace (size);
273 // If we have just overflowed the current block, we need to back up and try again.
274 if (G_UNLIKELY (pool->pos >= pool->end)) {
275 pool->pos -= size; // Back out
277 // For large objects, allocate the object into its own block.
278 // (In individual allocation mode, the constant will be 0 and this path will always be taken)
279 if (size >= MONO_MEMPOOL_PREFER_INDIVIDUAL_ALLOCATION_SIZE) {
280 guint new_size = SIZEOF_MEM_POOL + size;
281 MonoMemPool *np = (MonoMemPool *)g_malloc (new_size);
283 np->next = pool->next;
286 pool->d.allocated += new_size;
287 total_bytes_allocated += new_size;
289 rval = (guint8*)np + SIZEOF_MEM_POOL;
291 // Notice: any unused memory at the end of the old head becomes simply abandoned in this case until the mempool is freed (see Bugzilla #35136)
292 guint new_size = get_next_size (pool, size);
293 MonoMemPool *np = (MonoMemPool *)g_malloc (new_size);
295 np->next = pool->next;
298 pool->pos = (guint8*)np + SIZEOF_MEM_POOL;
299 pool->end = (guint8*)np + new_size;
300 pool->d.allocated += new_size;
301 total_bytes_allocated += new_size;
312 * mono_mempool_alloc0:
314 * same as mono_mempool_alloc, but fills memory with zero.
317 mono_mempool_alloc0 (MonoMemPool *pool, guint size)
321 // For the fast path, repeat the first few lines of mono_mempool_alloc
322 size = ALIGN_SIZE (size);
324 pool->pos = (guint8*)rval + size;
326 // If that doesn't work fall back on mono_mempool_alloc to handle new chunk allocation
327 if (G_UNLIKELY (pool->pos >= pool->end)) {
328 rval = mono_mempool_alloc (pool, size);
330 #ifdef TRACE_ALLOCATIONS
331 else if (pool == mono_get_corlib ()->mempool) {
332 mono_backtrace (size);
336 memset (rval, 0, size);
341 * mono_mempool_contains_addr:
343 * Determines whenever ADDR is inside the memory used by the mempool.
346 mono_mempool_contains_addr (MonoMemPool *pool,
349 MonoMemPool *p = pool;
352 if (addr >= (gpointer)p && addr < (gpointer)((guint8*)p + p->size))
361 * mono_mempool_strdup:
363 * Same as strdup, but allocates memory from the mempool.
364 * Returns: a pointer to the newly allocated string data inside the mempool.
367 mono_mempool_strdup (MonoMemPool *pool,
377 res = (char *)mono_mempool_alloc (pool, l + 1);
378 memcpy (res, s, l + 1);
384 * mono_mempool_get_allocated:
386 * Return the amount of memory allocated for this mempool.
389 mono_mempool_get_allocated (MonoMemPool *pool)
391 return pool->d.allocated;
395 * mono_mempool_get_bytes_allocated:
397 * Return the number of bytes currently allocated for mempools.
400 mono_mempool_get_bytes_allocated (void)
402 return total_bytes_allocated;