#include "gthread.h"
#include "glib_trace.h"
+#include "valgrind.h"
+
+/**
+ * SECTION:memory_slices
+ * @title: Memory Slices
+ * @short_description: efficient way to allocate groups of equal-sized
+ * chunks of memory
+ *
+ * Memory slices provide a space-efficient and multi-processing scalable
+ * way to allocate equal-sized pieces of memory, just like the original
+ * #GMemChunks (from GLib 2.8), while avoiding their excessive
+ * memory-waste, scalability and performance problems.
+ *
+ * To achieve these goals, the slice allocator uses a sophisticated,
+ * layered design that has been inspired by Bonwick's slab allocator
+ * <footnote><para>
+ * <ulink url="http://citeseer.ist.psu.edu/bonwick94slab.html">[Bonwick94]</ulink> Jeff Bonwick, The slab allocator: An object-caching kernel
+ * memory allocator. USENIX 1994, and
+ * <ulink url="http://citeseer.ist.psu.edu/bonwick01magazines.html">[Bonwick01]</ulink> Bonwick and Jonathan Adams, Magazines and vmem: Extending the
+ * slab allocator to many cpu's and arbitrary resources. USENIX 2001
+ * </para></footnote>.
+ * It uses posix_memalign() to optimize allocations of many equally-sized
+ * chunks, and has per-thread free lists (the so-called magazine layer)
+ * to quickly satisfy allocation requests of already known structure sizes.
+ * This is accompanied by extra caching logic to keep freed memory around
+ * for some time before returning it to the system. Memory that is unused
+ * due to alignment constraints is used for cache colorization (random
+ * distribution of chunk addresses) to improve CPU cache utilization. The
+ * caching layer of the slice allocator adapts itself to high lock contention
+ * to improve scalability.
+ *
+ * The slice allocator can allocate blocks as small as two pointers, and
+ * unlike malloc(), it does not reserve extra space per block. For large block
+ * sizes, g_slice_new() and g_slice_alloc() will automatically delegate to the
+ * system malloc() implementation. For newly written code it is recommended
+ * to use the new <literal>g_slice</literal> API instead of g_malloc() and
+ * friends, as long as objects are not resized during their lifetime and the
+ * object size used at allocation time is still available when freeing.
+ *
+ * <example>
+ * <title>Using the slice allocator</title>
+ * <programlisting>
+ * gchar *mem[10000];
+ * gint i;
+ *
+ * /* Allocate 10000 blocks. */
+ * for (i = 0; i < 10000; i++)
+ * {
+ * mem[i] = g_slice_alloc (50);
+ *
+ * /* Fill in the memory with some junk. */
+ * for (j = 0; j < 50; j++)
+ * mem[i][j] = i * j;
+ * }
+ *
+ * /* Now free all of the blocks. */
+ * for (i = 0; i < 10000; i++)
+ * {
+ * g_slice_free1 (50, mem[i]);
+ * }
+ * </programlisting></example>
+ *
+ * <example>
+ * <title>Using the slice allocator with data structures</title>
+ * <programlisting>
+ * GRealArray *array;
+ *
+ * /* Allocate one block, using the g_slice_new() macro. */
+ * array = g_slice_new (GRealArray);
+
+ * /* We can now use array just like a normal pointer to a structure. */
+ * array->data = NULL;
+ * array->len = 0;
+ * array->alloc = 0;
+ * array->zero_terminated = (zero_terminated ? 1 : 0);
+ * array->clear = (clear ? 1 : 0);
+ * array->elt_size = elt_size;
+ *
+ * /* We can free the block, so it can be reused. */
+ * g_slice_free (GRealArray, array);
+ * </programlisting></example>
+ */
+
/* the GSlice allocator is split up into 4 layers, roughly modelled after the slab
* allocator and magazine extensions as outlined in:
* + [Bonwick94] Jeff Bonwick, The slab allocator: An object-caching kernel
if (flags & (1 << 1))
config->debug_blocks = TRUE;
}
+ else
+ {
+ /* G_SLICE was not specified, so check if valgrind is running and
+ * disable ourselves if it is.
+ *
+ * This way it's possible to force gslice to be enabled under
+ * valgrind just by setting G_SLICE to the empty string.
+ */
+ if (RUNNING_ON_VALGRIND)
+ config->always_malloc = TRUE;
+ }
}
static void
* fit less than 8 times (see [4]) into 4KB pages.
* we allow very small page sizes here, to reduce wastage in
* threads if only small allocations are required (this does
- * bear the risk of incresing allocation times and fragmentation
+ * bear the risk of increasing allocation times and fragmentation
* though).
*/
allocator->min_page_size = MAX (allocator->min_page_size, 4096);
}
/* --- API functions --- */
+
+/**
+ * g_slice_new:
+ * @type: the type to allocate, typically a structure name
+ *
+ * A convenience macro to allocate a block of memory from the
+ * slice allocator.
+ *
+ * It calls g_slice_alloc() with <literal>sizeof (@type)</literal>
+ * and casts the returned pointer to a pointer of the given type,
+ * avoiding a type cast in the source code.
+ * Note that the underlying slice allocation mechanism can
+ * be changed with the <link linkend="G_SLICE">G_SLICE=always-malloc</link>
+ * environment variable.
+ *
+ * Returns: a pointer to the allocated block, cast to a pointer to @type
+ *
+ * Since: 2.10
+ */
+
+/**
+ * g_slice_new0:
+ * @type: the type to allocate, typically a structure name
+ *
+ * A convenience macro to allocate a block of memory from the
+ * slice allocator and set the memory to 0.
+ *
+ * It calls g_slice_alloc0() with <literal>sizeof (@type)</literal>
+ * and casts the returned pointer to a pointer of the given type,
+ * avoiding a type cast in the source code.
+ * Note that the underlying slice allocation mechanism can
+ * be changed with the <link linkend="G_SLICE">G_SLICE=always-malloc</link>
+ * environment variable.
+ *
+ * Since: 2.10
+ */
+
+/**
+ * g_slice_dup:
+ * @type: the type to duplicate, typically a structure name
+ * @mem: the memory to copy into the allocated block
+ *
+ * A convenience macro to duplicate a block of memory using
+ * the slice allocator.
+ *
+ * It calls g_slice_copy() with <literal>sizeof (@type)</literal>
+ * and casts the returned pointer to a pointer of the given type,
+ * avoiding a type cast in the source code.
+ * Note that the underlying slice allocation mechanism can
+ * be changed with the <link linkend="G_SLICE">G_SLICE=always-malloc</link>
+ * environment variable.
+ *
+ * Returns: a pointer to the allocated block, cast to a pointer to @type
+ *
+ * Since: 2.14
+ */
+
+/**
+ * g_slice_free:
+ * @type: the type of the block to free, typically a structure name
+ * @mem: a pointer to the block to free
+ *
+ * A convenience macro to free a block of memory that has
+ * been allocated from the slice allocator.
+ *
+ * It calls g_slice_free1() using <literal>sizeof (type)</literal>
+ * as the block size.
+ * Note that the exact release behaviour can be changed with the
+ * <link linkend="G_DEBUG">G_DEBUG=gc-friendly</link> environment
+ * variable, also see <link linkend="G_SLICE">G_SLICE</link> for
+ * related debugging options.
+ *
+ * Since: 2.10
+ */
+
+/**
+ * g_slice_free_chain:
+ * @type: the type of the @mem_chain blocks
+ * @mem_chain: a pointer to the first block of the chain
+ * @next: the field name of the next pointer in @type
+ *
+ * Frees a linked list of memory blocks of structure type @type.
+ * The memory blocks must be equal-sized, allocated via
+ * g_slice_alloc() or g_slice_alloc0() and linked together by
+ * a @next pointer (similar to #GSList). The name of the
+ * @next field in @type is passed as third argument.
+ * Note that the exact release behaviour can be changed with the
+ * <link linkend="G_DEBUG">G_DEBUG=gc-friendly</link> environment
+ * variable, also see <link linkend="G_SLICE">G_SLICE</link> for
+ * related debugging options.
+ *
+ * Since: 2.10
+ */
+
+/**
+ * g_slice_alloc:
+ * @block_size: the number of bytes to allocate
+ *
+ * Allocates a block of memory from the slice allocator.
+ * The block adress handed out can be expected to be aligned
+ * to at least <literal>1 * sizeof (void*)</literal>,
+ * though in general slices are 2 * sizeof (void*) bytes aligned,
+ * if a malloc() fallback implementation is used instead,
+ * the alignment may be reduced in a libc dependent fashion.
+ * Note that the underlying slice allocation mechanism can
+ * be changed with the <link linkend="G_SLICE">G_SLICE=always-malloc</link>
+ * environment variable.
+ *
+ * Returns: a pointer to the allocated memory block
+ *
+ * Since: 2.10
+ */
gpointer
g_slice_alloc (gsize mem_size)
{
return mem;
}
+/**
+ * g_slice_alloc0:
+ * @block_size: the number of bytes to allocate
+ *
+ * Allocates a block of memory via g_slice_alloc() and initializes
+ * the returned memory to 0. Note that the underlying slice allocation
+ * mechanism can be changed with the
+ * <link linkend="G_SLICE">G_SLICE=always-malloc</link>
+ * environment variable.
+ *
+ * Returns: a pointer to the allocated block
+ *
+ * Since: 2.10
+ */
gpointer
g_slice_alloc0 (gsize mem_size)
{
return mem;
}
+/**
+ * g_slice_copy:
+ * @block_size: the number of bytes to allocate
+ * @mem_block: the memory to copy
+ *
+ * Allocates a block of memory from the slice allocator
+ * and copies @block_size bytes into it from @mem_block.
+ *
+ * Returns: a pointer to the allocated memory block
+ *
+ * Since: 2.14
+ */
gpointer
g_slice_copy (gsize mem_size,
gconstpointer mem_block)
return mem;
}
+/**
+ * g_slice_free1:
+ * @block_size: the size of the block
+ * @mem_block: a pointer to the block to free
+ *
+ * Frees a block of memory.
+ *
+ * The memory must have been allocated via g_slice_alloc() or
+ * g_slice_alloc0() and the @block_size has to match the size
+ * specified upon allocation. Note that the exact release behaviour
+ * can be changed with the
+ * <link linkend="G_DEBUG">G_DEBUG=gc-friendly</link> environment
+ * variable, also see <link linkend="G_SLICE">G_SLICE</link> for
+ * related debugging options.
+ *
+ * Since: 2.10
+ */
void
g_slice_free1 (gsize mem_size,
gpointer mem_block)
TRACE (GLIB_SLICE_FREE((void*)mem_block, mem_size));
}
+/**
+ * g_slice_free_chain_with_offset:
+ * @block_size: the size of the blocks
+ * @mem_chain: a pointer to the first block of the chain
+ * @next_offset: the offset of the @next field in the blocks
+ *
+ * Frees a linked list of memory blocks of structure type @type.
+ *
+ * The memory blocks must be equal-sized, allocated via
+ * g_slice_alloc() or g_slice_alloc0() and linked together by a
+ * @next pointer (similar to #GSList). The offset of the @next
+ * field in each block is passed as third argument.
+ * Note that the exact release behaviour can be changed with the
+ * <link linkend="G_DEBUG">G_DEBUG=gc-friendly</link> environment
+ * variable, also see <link linkend="G_SLICE">G_SLICE</link> for
+ * related debugging options.
+ *
+ * Since: 2.10
+ */
void
g_slice_free_chain_with_offset (gsize mem_size,
gpointer mem_chain,
/* --- g-slice memory checker tree implementation --- */
#define SMC_TRUNK_COUNT (4093 /* 16381 */) /* prime, to distribute trunk collisions (big, allocated just once) */
#define SMC_BRANCH_COUNT (511) /* prime, to distribute branch collisions */
-#define SMC_TRUNK_EXTENT (SMC_BRANCH_COUNT * 2039) /* key adress space per trunk, should distribute uniformly across BRANCH_COUNT */
+#define SMC_TRUNK_EXTENT (SMC_BRANCH_COUNT * 2039) /* key address space per trunk, should distribute uniformly across BRANCH_COUNT */
#define SMC_TRUNK_HASH(k) ((k / SMC_TRUNK_EXTENT) % SMC_TRUNK_COUNT) /* generate new trunk hash per megabyte (roughly) */
#define SMC_BRANCH_HASH(k) (k % SMC_BRANCH_COUNT)
projects / platform / upstream / glib.git / blobdiff