mariadb/mem/mem0mem.c

/************************************************************************
The memory management

(c) 1994, 1995 Innobase Oy

Created 6/9/1994 Heikki Tuuri
*************************************************************************/


#include "mem0mem.h"
#ifdef UNIV_NONINL
#include "mem0mem.ic"
#endif

#include "mach0data.h"
#include "buf0buf.h"
#include "mem0dbg.c"
#include <stdarg.h>

/*
			THE MEMORY MANAGEMENT
			=====================

The basic element of the memory management is called a memory
heap. A memory heap is conceptually a
stack from which memory can be allocated. The stack may grow infinitely.
The top element of the stack may be freed, or
the whole stack can be freed at one time. The advantage of the
memory heap concept is that we can avoid using the malloc and free
functions of C which are quite expensive, for example, on the Solaris + GCC
system (50 MHz Sparc, 1993) the pair takes 3 microseconds,
on Win NT + 100MHz Pentium, 2.5 microseconds.
When we use a memory heap,
we can allocate larger blocks of memory at a time and thus
reduce overhead. Slightly more efficient the method is when we
allocate the memory from the index page buffer pool, as we can
claim a new page fast. This is called buffer allocation.
When we allocate the memory from the dynamic memory of the
C environment, that is called dynamic allocation.

The default way of operation of the memory heap is the following.
First, when the heap is created, an initial block of memory is
allocated. In dynamic allocation this may be about 50 bytes.
If more space is needed, additional blocks are allocated
and they are put into a linked list.
After the initial block, each allocated block is twice the size of the
previous, until a threshold is attained, after which the sizes
of the blocks stay the same. An exception is, of course, the case
where the caller requests a memory buffer whose size is
bigger than the threshold. In that case a block big enough must
be allocated.

The heap is physically arranged so that if the current block
becomes full, a new block is allocated and always inserted in the
chain of blocks as the last block.

In the debug version of the memory management, all the allocated
heaps are kept in a list (which is implemented as a hash table).
Thus we can notice if the caller tries to free an already freed
heap. In addition, each buffer given to the caller contains
start field at the start and a trailer field at the end of the buffer.

The start field has the following content:
A. sizeof(ulint) bytes of field length (in the standard byte order)
B. sizeof(ulint) bytes of check field (a random number)

The trailer field contains:
A. sizeof(ulint) bytes of check field (the same random number as at the start)

Thus we can notice if something has been copied over the
borders of the buffer, which is illegal.
The memory in the buffers is initialized to a random byte sequence.
After freeing, all the blocks in the heap are set to random bytes
to help us discover errors which result from the use of
buffers in an already freed heap. */

#ifdef MEM_PERIODIC_CHECK

ibool					mem_block_list_inited;
/* List of all mem blocks allocated; protected by the mem_comm_pool mutex */
UT_LIST_BASE_NODE_T(mem_block_t)	mem_block_list;

#endif

/**************************************************************************
Duplicates a NUL-terminated string, allocated from a memory heap. */
UNIV_INTERN
char*
mem_heap_strdup(
/*============*/
				/* out, own: a copy of the string */
	mem_heap_t*	heap,	/* in: memory heap where string is allocated */
	const char*	str)	/* in: string to be copied */
{
	return(mem_heap_dup(heap, str, strlen(str) + 1));
}

/**************************************************************************
Duplicate a block of data, allocated from a memory heap. */
UNIV_INTERN
void*
mem_heap_dup(
/*=========*/
				/* out, own: a copy of the data */
	mem_heap_t*	heap,	/* in: memory heap where copy is allocated */
	const void*	data,	/* in: data to be copied */
	ulint		len)	/* in: length of data, in bytes */
{
	return(memcpy(mem_heap_alloc(heap, len), data, len));
}

/**************************************************************************
Concatenate two memory blocks and return the result, using a memory heap. */
UNIV_INTERN
void*
mem_heap_cat(
/*=========*/
				/* out, own: the result */
	mem_heap_t*	heap,	/* in: memory heap where result is allocated */
	const void*	b1,	/* in: block 1 */
	ulint		len1,	/* in: length of b1, in bytes */
	const void*	b2,	/* in: block 2 */
	ulint		len2)	/* in: length of b2, in bytes */
{
	void*	res = mem_heap_alloc(heap, len1 + len2);

	memcpy(res, b1, len1);
	memcpy((char*)res + len1, b2, len2);

	return(res);
}

/**************************************************************************
Concatenate two strings and return the result, using a memory heap. */
UNIV_INTERN
char*
mem_heap_strcat(
/*============*/
				/* out, own: the result */
	mem_heap_t*	heap,	/* in: memory heap where string is allocated */
	const char*	s1,	/* in: string 1 */
	const char*	s2)	/* in: string 2 */
{
	char*	s;
	ulint	s1_len = strlen(s1);
	ulint	s2_len = strlen(s2);

	s = mem_heap_alloc(heap, s1_len + s2_len + 1);

	memcpy(s, s1, s1_len);
	memcpy(s + s1_len, s2, s2_len);

	s[s1_len + s2_len] = '\0';

	return(s);
}


/********************************************************************
Helper function for mem_heap_printf. */
static
ulint
mem_heap_printf_low(
/*================*/
				/* out: length of formatted string,
				including terminating NUL */
	char*		buf,	/* in/out: buffer to store formatted string
				in, or NULL to just calculate length */
	const char*	format,	/* in: format string */
	va_list		ap)	/* in: arguments */
{
	ulint 		len = 0;

	while (*format) {

		/* Does this format specifier have the 'l' length modifier. */
		ibool	is_long = FALSE;

		/* Length of one parameter. */
		size_t	plen;

		if (*format++ != '%') {
			/* Non-format character. */

			len++;

			if (buf) {
				*buf++ = *(format - 1);
			}

			continue;
		}

		if (*format == 'l') {
			is_long = TRUE;
			format++;
		}

		switch (*format++) {
		case 's':
			/* string */
			{
				char*	s = va_arg(ap, char*);

				/* "%ls" is a non-sensical format specifier. */
				ut_a(!is_long);

				plen = strlen(s);
				len += plen;

				if (buf) {
					memcpy(buf, s, plen);
					buf += plen;
				}
			}

			break;

		case 'u':
			/* unsigned int */
			{
				char		tmp[32];
				unsigned long	val;

				/* We only support 'long' values for now. */
				ut_a(is_long);

				val = va_arg(ap, unsigned long);

				plen = sprintf(tmp, "%lu", val);
				len += plen;

				if (buf) {
					memcpy(buf, tmp, plen);
					buf += plen;
				}
			}

			break;

		case '%':

			/* "%l%" is a non-sensical format specifier. */
			ut_a(!is_long);

			len++;

			if (buf) {
				*buf++ = '%';
			}

			break;

		default:
			ut_error;
		}
	}

	/* For the NUL character. */
	len++;

	if (buf) {
		*buf = '\0';
	}

	return(len);
}

/********************************************************************
A simple (s)printf replacement that dynamically allocates the space for the
formatted string from the given heap. This supports a very limited set of
the printf syntax: types 's' and 'u' and length modifier 'l' (which is
required for the 'u' type). */
UNIV_INTERN
char*
mem_heap_printf(
/*============*/
				/* out: heap-allocated formatted string */
	mem_heap_t*	heap,	/* in: memory heap */
	const char*	format,	/* in: format string */
	...)
{
	va_list		ap;
	char*		str;
	ulint 		len;

	/* Calculate length of string */
	len = 0;
	va_start(ap, format);
	len = mem_heap_printf_low(NULL, format, ap);
	va_end(ap);

	/* Now create it for real. */
	str = mem_heap_alloc(heap, len);
	va_start(ap, format);
	mem_heap_printf_low(str, format, ap);
	va_end(ap);

	return(str);
}

/*******************************************************************
Creates a memory heap block where data can be allocated. */
UNIV_INTERN
mem_block_t*
mem_heap_create_block(
/*==================*/
				/* out, own: memory heap block, NULL if
				did not succeed (only possible for
				MEM_HEAP_BTR_SEARCH type heaps) */
	mem_heap_t*	heap,	/* in: memory heap or NULL if first block
				should be created */
	ulint		n,	/* in: number of bytes needed for user data */
	ulint		type,	/* in: type of heap: MEM_HEAP_DYNAMIC or
				MEM_HEAP_BUFFER */
	const char*	file_name,/* in: file name where created */
	ulint		line)	/* in: line where created */
{
	buf_block_t*	buf_block = NULL;
	mem_block_t*	block;
	ulint		len;

	ut_ad((type == MEM_HEAP_DYNAMIC) || (type == MEM_HEAP_BUFFER)
	      || (type == MEM_HEAP_BUFFER + MEM_HEAP_BTR_SEARCH));

	if (heap && heap->magic_n != MEM_BLOCK_MAGIC_N) {
		mem_analyze_corruption(heap);
	}

	/* In dynamic allocation, calculate the size: block header + data. */
	len = MEM_BLOCK_HEADER_SIZE + MEM_SPACE_NEEDED(n);

	if (type == MEM_HEAP_DYNAMIC || len < UNIV_PAGE_SIZE / 2) {

		ut_ad(type == MEM_HEAP_DYNAMIC || n <= MEM_MAX_ALLOC_IN_BUF);

		block = mem_area_alloc(&len, mem_comm_pool);
	} else {
		len = UNIV_PAGE_SIZE;

		if ((type & MEM_HEAP_BTR_SEARCH) && heap) {
			/* We cannot allocate the block from the
			buffer pool, but must get the free block from
			the heap header free block field */

			buf_block = heap->free_block;
			heap->free_block = NULL;

			if (UNIV_UNLIKELY(!buf_block)) {

				return(NULL);
			}
		} else {
			buf_block = buf_block_alloc(0);
		}

		block = (mem_block_t*) buf_block->frame;
	}

	ut_ad(block);
	block->buf_block = buf_block;
	block->magic_n = MEM_BLOCK_MAGIC_N;
	ut_strlcpy_rev(block->file_name, file_name, sizeof(block->file_name));
	block->line = line;

#ifdef MEM_PERIODIC_CHECK
	mem_pool_mutex_enter();

	if (!mem_block_list_inited) {
		mem_block_list_inited = TRUE;
		UT_LIST_INIT(mem_block_list);
	}

	UT_LIST_ADD_LAST(mem_block_list, mem_block_list, block);

	mem_pool_mutex_exit();
#endif
	mem_block_set_len(block, len);
	mem_block_set_type(block, type);
	mem_block_set_free(block, MEM_BLOCK_HEADER_SIZE);
	mem_block_set_start(block, MEM_BLOCK_HEADER_SIZE);

	block->free_block = NULL;

	ut_ad((ulint)MEM_BLOCK_HEADER_SIZE < len);

	return(block);
}

/*******************************************************************
Adds a new block to a memory heap. */
UNIV_INTERN
mem_block_t*
mem_heap_add_block(
/*===============*/
				/* out: created block, NULL if did not
				succeed (only possible for
				MEM_HEAP_BTR_SEARCH type heaps)*/
	mem_heap_t*	heap,	/* in: memory heap */
	ulint		n)	/* in: number of bytes user needs */
{
	mem_block_t*	block;
	mem_block_t*	new_block;
	ulint		new_size;

	ut_ad(mem_heap_check(heap));

	block = UT_LIST_GET_LAST(heap->base);

	/* We have to allocate a new block. The size is always at least
	doubled until the standard size is reached. After that the size
	stays the same, except in cases where the caller needs more space. */

	new_size = 2 * mem_block_get_len(block);

	if (heap->type != MEM_HEAP_DYNAMIC) {
		/* From the buffer pool we allocate buffer frames */
		ut_a(n <= MEM_MAX_ALLOC_IN_BUF);

		if (new_size > MEM_MAX_ALLOC_IN_BUF) {
			new_size = MEM_MAX_ALLOC_IN_BUF;
		}
	} else if (new_size > MEM_BLOCK_STANDARD_SIZE) {

		new_size = MEM_BLOCK_STANDARD_SIZE;
	}

	if (new_size < n) {
		new_size = n;
	}

	new_block = mem_heap_create_block(heap, new_size, heap->type,
					  heap->file_name, heap->line);
	if (new_block == NULL) {

		return(NULL);
	}

	/* Add the new block as the last block */

	UT_LIST_INSERT_AFTER(list, heap->base, block, new_block);

	return(new_block);
}

/**********************************************************************
Frees a block from a memory heap. */
UNIV_INTERN
void
mem_heap_block_free(
/*================*/
	mem_heap_t*	heap,	/* in: heap */
	mem_block_t*	block)	/* in: block to free */
{
	ulint		type;
	ulint		len;
	buf_block_t*	buf_block;

	if (block->magic_n != MEM_BLOCK_MAGIC_N) {
		mem_analyze_corruption(block);
	}

	UT_LIST_REMOVE(list, heap->base, block);

#ifdef MEM_PERIODIC_CHECK
	mem_pool_mutex_enter();

	UT_LIST_REMOVE(mem_block_list, mem_block_list, block);

	mem_pool_mutex_exit();
#endif
	type = heap->type;
	len = block->len;
	buf_block = block->buf_block;
	block->magic_n = MEM_FREED_BLOCK_MAGIC_N;

#ifdef UNIV_MEM_DEBUG
	/* In the debug version we set the memory to a random combination
	of hex 0xDE and 0xAD. */

	mem_erase_buf((byte*)block, len);
#else /* UNIV_MEM_DEBUG */
	UNIV_MEM_ASSERT_AND_FREE(block, len);
#endif /* UNIV_MEM_DEBUG */

	if (type == MEM_HEAP_DYNAMIC || len < UNIV_PAGE_SIZE / 2) {

		ut_ad(!buf_block);
		mem_area_free(block, mem_comm_pool);
	} else {
		ut_ad(type & MEM_HEAP_BUFFER);

		buf_block_free(buf_block);
	}
}

/**********************************************************************
Frees the free_block field from a memory heap. */
UNIV_INTERN
void
mem_heap_free_block_free(
/*=====================*/
	mem_heap_t*	heap)	/* in: heap */
{
	if (UNIV_LIKELY_NULL(heap->free_block)) {

		buf_block_free(heap->free_block);

		heap->free_block = NULL;
	}
}

#ifdef MEM_PERIODIC_CHECK
/**********************************************************************
Goes through the list of all allocated mem blocks, checks their magic
numbers, and reports possible corruption. */
UNIV_INTERN
void
mem_validate_all_blocks(void)
/*=========================*/
{
	mem_block_t*	block;

	mem_pool_mutex_enter();

	block = UT_LIST_GET_FIRST(mem_block_list);

	while (block) {
		if (block->magic_n != MEM_BLOCK_MAGIC_N) {
			mem_analyze_corruption(block);
		}

		block = UT_LIST_GET_NEXT(mem_block_list, block);
	}

	mem_pool_mutex_exit();
}
#endif