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)
183 still_free = pool->end - pool->pos;
184 g_print ("Mempool %p stats:\n", pool);
185 g_print ("Total mem allocated: %d\n", pool->d.allocated);
186 g_print ("Num chunks: %d\n", count);
187 g_print ("Free memory: %d\n", still_free);
191 #ifdef TRACE_ALLOCATIONS
192 #include <execinfo.h>
193 #include "metadata/appdomain.h"
194 #include "metadata/metadata-internals.h"
196 static mono_mutex_t mempool_tracing_lock;
197 #define BACKTRACE_DEPTH 7
199 mono_backtrace (int size)
201 void *array[BACKTRACE_DEPTH];
204 static gboolean inited;
207 mono_os_mutex_init_recursive (&mempool_tracing_lock);
211 mono_os_mutex_lock (&mempool_tracing_lock);
212 g_print ("Allocating %d bytes\n", size);
213 symbols = backtrace (array, BACKTRACE_DEPTH);
214 names = backtrace_symbols (array, symbols);
215 for (i = 1; i < symbols; ++i) {
216 g_print ("\t%s\n", names [i]);
219 mono_os_mutex_unlock (&mempool_tracing_lock);
225 * mono_mempool_alloc:
226 * @pool: the memory pool to use
227 * @size: size of the memory entity we are trying to allocate
229 * A mempool is growing; give a recommended size for the next block.
230 * Each block in a mempool should be about 150% bigger than the previous one,
231 * or bigger if it is necessary to include the new entity.
233 * Returns: the recommended size.
236 get_next_size (MonoMemPool *pool, int size)
238 int target = pool->next? pool->next->size: pool->size;
239 size += SIZEOF_MEM_POOL;
240 /* increase the size */
241 target += target / 2;
242 while (target < size) {
243 target += target / 2;
245 if (target > MONO_MEMPOOL_PAGESIZE && size <= MONO_MEMPOOL_PAGESIZE)
246 target = MONO_MEMPOOL_PAGESIZE;
251 * mono_mempool_alloc:
252 * @pool: the memory pool to use
253 * @size: size of the memory block
255 * Allocates a new block of memory in @pool.
257 * Returns: the address of a newly allocated memory block.
260 mono_mempool_alloc (MonoMemPool *pool, guint size)
262 gpointer rval = pool->pos; // Return value
264 // Normal case: Just bump up pos pointer and we are done
265 size = ALIGN_SIZE (size);
266 pool->pos = (guint8*)rval + size;
268 #ifdef TRACE_ALLOCATIONS
269 if (pool == mono_get_corlib ()->mempool) {
270 mono_backtrace (size);
274 // If we have just overflowed the current block, we need to back up and try again.
275 if (G_UNLIKELY (pool->pos >= pool->end)) {
276 pool->pos -= size; // Back out
278 // For large objects, allocate the object into its own block.
279 // (In individual allocation mode, the constant will be 0 and this path will always be taken)
280 if (size >= MONO_MEMPOOL_PREFER_INDIVIDUAL_ALLOCATION_SIZE) {
281 guint new_size = SIZEOF_MEM_POOL + size;
282 MonoMemPool *np = (MonoMemPool *)g_malloc (new_size);
284 np->next = pool->next;
287 pool->d.allocated += new_size;
288 total_bytes_allocated += new_size;
290 rval = (guint8*)np + SIZEOF_MEM_POOL;
292 // 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)
293 guint new_size = get_next_size (pool, size);
294 MonoMemPool *np = (MonoMemPool *)g_malloc (new_size);
296 np->next = pool->next;
299 pool->pos = (guint8*)np + SIZEOF_MEM_POOL;
300 pool->end = (guint8*)np + new_size;
301 pool->d.allocated += new_size;
302 total_bytes_allocated += new_size;
313 * mono_mempool_alloc0:
315 * same as mono_mempool_alloc, but fills memory with zero.
318 mono_mempool_alloc0 (MonoMemPool *pool, guint size)
322 // For the fast path, repeat the first few lines of mono_mempool_alloc
323 size = ALIGN_SIZE (size);
325 pool->pos = (guint8*)rval + size;
327 // If that doesn't work fall back on mono_mempool_alloc to handle new chunk allocation
328 if (G_UNLIKELY (pool->pos >= pool->end)) {
329 rval = mono_mempool_alloc (pool, size);
331 #ifdef TRACE_ALLOCATIONS
332 else if (pool == mono_get_corlib ()->mempool) {
333 mono_backtrace (size);
337 memset (rval, 0, size);
342 * mono_mempool_contains_addr:
344 * Determines whenever ADDR is inside the memory used by the mempool.
347 mono_mempool_contains_addr (MonoMemPool *pool,
350 MonoMemPool *p = pool;
353 if (addr >= (gpointer)p && addr < (gpointer)((guint8*)p + p->size))
362 * mono_mempool_strdup:
364 * Same as strdup, but allocates memory from the mempool.
365 * Returns: a pointer to the newly allocated string data inside the mempool.
368 mono_mempool_strdup (MonoMemPool *pool,
378 res = (char *)mono_mempool_alloc (pool, l + 1);
379 memcpy (res, s, l + 1);
385 * mono_mempool_get_allocated:
387 * Return the amount of memory allocated for this mempool.
390 mono_mempool_get_allocated (MonoMemPool *pool)
392 return pool->d.allocated;
396 * mono_mempool_get_bytes_allocated:
398 * Return the number of bytes currently allocated for mempools.
401 mono_mempool_get_bytes_allocated (void)
403 return total_bytes_allocated;