path: root/storage/xtradb/buf/buf0buddy.c

/*****************************************************************************

Copyright (c) 2006, 2011, Oracle and/or its affiliates. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA 02111-1307 USA

*****************************************************************************/

/**************************************************//**
@file buf/buf0buddy.c
Binary buddy allocator for compressed pages

Created December 2006 by Marko Makela
*******************************************************/

#define THIS_MODULE
#include "buf0buddy.h"
#ifdef UNIV_NONINL
# include "buf0buddy.ic"
#endif
#undef THIS_MODULE
#include "buf0buf.h"
#include "buf0lru.h"
#include "buf0flu.h"
#include "page0zip.h"

/* Statistic counters */

#ifdef UNIV_DEBUG
/** Number of frames allocated from the buffer pool to the buddy system.
Protected by buf_pool_mutex. */
static ulint buf_buddy_n_frames;
#endif /* UNIV_DEBUG */
/** Statistics of the buddy system, indexed by block size.
Protected by buf_pool_mutex. */
UNIV_INTERN buf_buddy_stat_t buf_buddy_stat[BUF_BUDDY_SIZES_MAX + 1];

/** Validate a given zip_free list. */
#define BUF_BUDDY_LIST_VALIDATE(i)				\
	UT_LIST_VALIDATE(zip_list, buf_page_t,			\
			 buf_pool->zip_free[i],			\
			 ut_ad(buf_page_get_state(		\
				       ut_list_node_313)	\
			       == BUF_BLOCK_ZIP_FREE))

/**********************************************************************//**
Get the offset of the buddy of a compressed page frame.
@return	the buddy relative of page */
UNIV_INLINE
byte*
buf_buddy_get(
/*==========*/
	byte*	page,	/*!< in: compressed page */
	ulint	size)	/*!< in: page size in bytes */
{
	ut_ad(ut_is_2pow(size));
	ut_ad(size >= BUF_BUDDY_LOW);
	ut_ad(size < BUF_BUDDY_HIGH);
	ut_ad(!ut_align_offset(page, size));

	if (((ulint) page) & size) {
		return(page - size);
	} else {
		return(page + size);
	}
}

/**********************************************************************//**
Add a block to the head of the appropriate buddy free list. */
UNIV_INLINE
void
buf_buddy_add_to_free(
/*==================*/
	buf_page_t*	bpage,	/*!< in,own: block to be freed */
	ulint		i)	/*!< in: index of buf_pool->zip_free[] */
{
	//ut_ad(buf_pool_mutex_own());
	ut_ad(mutex_own(&zip_free_mutex));
	ut_ad(buf_page_get_state(bpage) == BUF_BLOCK_ZIP_FREE);
	ut_ad(buf_pool->zip_free[i].start != bpage);
	UT_LIST_ADD_FIRST(zip_list, buf_pool->zip_free[i], bpage);
}

/**********************************************************************//**
Remove a block from the appropriate buddy free list. */
UNIV_INLINE
void
buf_buddy_remove_from_free(
/*=======================*/
	buf_page_t*	bpage,	/*!< in: block to be removed */
	ulint		i)	/*!< in: index of buf_pool->zip_free[] */
{
#ifdef UNIV_DEBUG
	buf_page_t*	prev = UT_LIST_GET_PREV(zip_list, bpage);
	buf_page_t*	next = UT_LIST_GET_NEXT(zip_list, bpage);

	ut_ad(!prev || buf_page_get_state(prev) == BUF_BLOCK_ZIP_FREE);
	ut_ad(!next || buf_page_get_state(next) == BUF_BLOCK_ZIP_FREE);
#endif /* UNIV_DEBUG */

	//ut_ad(buf_pool_mutex_own());
	ut_ad(mutex_own(&zip_free_mutex));
	ut_ad(buf_page_get_state(bpage) == BUF_BLOCK_ZIP_FREE);
	UT_LIST_REMOVE(zip_list, buf_pool->zip_free[i], bpage);
}

/**********************************************************************//**
Try to allocate a block from buf_pool->zip_free[].
@return	allocated block, or NULL if buf_pool->zip_free[] was empty */
static
void*
buf_buddy_alloc_zip(
/*================*/
	ulint	i)	/*!< in: index of buf_pool->zip_free[] */
{
	buf_page_t*	bpage;

	//ut_ad(buf_pool_mutex_own());
	ut_ad(mutex_own(&zip_free_mutex));
	ut_a(i < BUF_BUDDY_SIZES);
	ut_a(i >= buf_buddy_get_slot(PAGE_ZIP_MIN_SIZE));

	ut_d(BUF_BUDDY_LIST_VALIDATE(i));

	bpage = UT_LIST_GET_LAST(buf_pool->zip_free[i]);

	if (bpage) {
		ut_a(buf_page_get_state(bpage) == BUF_BLOCK_ZIP_FREE);

		buf_buddy_remove_from_free(bpage, i);
	} else if (i + 1 < BUF_BUDDY_SIZES) {
		/* Attempt to split. */
		bpage = buf_buddy_alloc_zip(i + 1);

		if (bpage) {
			buf_page_t*	buddy = (buf_page_t*)
				(((char*) bpage) + (BUF_BUDDY_LOW << i));

			ut_ad(!buf_pool_contains_zip(buddy));
			ut_d(memset(buddy, i, BUF_BUDDY_LOW << i));
			buddy->state = BUF_BLOCK_ZIP_FREE;
			buf_buddy_add_to_free(buddy, i);
		}
	}

	if (bpage) {
		ut_d(memset(bpage, ~i, BUF_BUDDY_LOW << i));
		UNIV_MEM_ALLOC(bpage, BUF_BUDDY_SIZES << i);
	}

	return(bpage);
}

/**********************************************************************//**
Deallocate a buffer frame of UNIV_PAGE_SIZE. */
static
void
buf_buddy_block_free(
/*=================*/
	void*	buf,	/*!< in: buffer frame to deallocate */
	ibool	have_page_hash_mutex)
{
	const ulint	fold	= BUF_POOL_ZIP_FOLD_PTR(buf);
	buf_page_t*	bpage;
	buf_block_t*	block;

	//ut_ad(buf_pool_mutex_own());
	ut_ad(!mutex_own(&buf_pool_zip_mutex));
	ut_a(!ut_align_offset(buf, UNIV_PAGE_SIZE));

	mutex_enter(&zip_hash_mutex);

	HASH_SEARCH(hash, buf_pool->zip_hash, fold, buf_page_t*, bpage,
		    ut_ad(buf_page_get_state(bpage) == BUF_BLOCK_MEMORY
			  && bpage->in_zip_hash && !bpage->in_page_hash),
		    ((buf_block_t*) bpage)->frame == buf);
	ut_a(bpage);
	ut_a(buf_page_get_state(bpage) == BUF_BLOCK_MEMORY);
	ut_ad(!bpage->in_page_hash);
	ut_ad(bpage->in_zip_hash);
	ut_d(bpage->in_zip_hash = FALSE);
	HASH_DELETE(buf_page_t, hash, buf_pool->zip_hash, fold, bpage);

	mutex_exit(&zip_hash_mutex);

	ut_d(memset(buf, 0, UNIV_PAGE_SIZE));
	UNIV_MEM_INVALID(buf, UNIV_PAGE_SIZE);

	block = (buf_block_t*) bpage;
	mutex_enter(&block->mutex);
	buf_LRU_block_free_non_file_page(block, have_page_hash_mutex);
	mutex_exit(&block->mutex);

	ut_ad(buf_buddy_n_frames > 0);
	ut_d(buf_buddy_n_frames--);
}

/**********************************************************************//**
Allocate a buffer block to the buddy allocator. */
static
void
buf_buddy_block_register(
/*=====================*/
	buf_block_t*	block)	/*!< in: buffer frame to allocate */
{
	const ulint	fold = BUF_POOL_ZIP_FOLD(block);
	//ut_ad(buf_pool_mutex_own());
	ut_ad(!mutex_own(&buf_pool_zip_mutex));
	ut_ad(buf_block_get_state(block) == BUF_BLOCK_READY_FOR_USE);

	buf_block_set_state(block, BUF_BLOCK_MEMORY);

	ut_a(block->frame);
	ut_a(!ut_align_offset(block->frame, UNIV_PAGE_SIZE));

	ut_ad(!block->page.in_page_hash);
	ut_ad(!block->page.in_zip_hash);
	ut_d(block->page.in_zip_hash = TRUE);

	mutex_enter(&zip_hash_mutex);
	HASH_INSERT(buf_page_t, hash, buf_pool->zip_hash, fold, &block->page);
	mutex_exit(&zip_hash_mutex);

	ut_d(buf_buddy_n_frames++);
}

/**********************************************************************//**
Allocate a block from a bigger object.
@return	allocated block */
static
void*
buf_buddy_alloc_from(
/*=================*/
	void*		buf,	/*!< in: a block that is free to use */
	ulint		i,	/*!< in: index of buf_pool->zip_free[] */
	ulint		j)	/*!< in: size of buf as an index
				of buf_pool->zip_free[] */
{
	ulint	offs	= BUF_BUDDY_LOW << j;
	ut_ad(j <= BUF_BUDDY_SIZES);
	ut_ad(i >= buf_buddy_get_slot(PAGE_ZIP_MIN_SIZE));
	ut_ad(j >= i);
	ut_ad(!ut_align_offset(buf, offs));

	/* Add the unused parts of the block to the free lists. */
	while (j > i) {
		buf_page_t*	bpage;

		offs >>= 1;
		j--;

		bpage = (buf_page_t*) ((byte*) buf + offs);
		ut_d(memset(bpage, j, BUF_BUDDY_LOW << j));
		bpage->state = BUF_BLOCK_ZIP_FREE;
		ut_d(BUF_BUDDY_LIST_VALIDATE(i));
		buf_buddy_add_to_free(bpage, j);
	}

	return(buf);
}

/**********************************************************************//**
Allocate a block.  The thread calling this function must hold
buf_pool_mutex and must not hold buf_pool_zip_mutex or any block->mutex.
The buf_pool_mutex may be released and reacquired.
@return	allocated block, never NULL */
UNIV_INTERN
void*
buf_buddy_alloc_low(
/*================*/
	ulint	i,	/*!< in: index of buf_pool->zip_free[],
			or BUF_BUDDY_SIZES */
	ibool*	lru,	/*!< in: pointer to a variable that will be assigned
			TRUE if storage was allocated from the LRU list
			and buf_pool_mutex was temporarily released */
	ibool	have_page_hash_mutex)
{
	buf_block_t*	block;

	ut_ad(lru);
	//ut_ad(buf_pool_mutex_own());
	ut_ad(!mutex_own(&buf_pool_zip_mutex));
	ut_ad(i >= buf_buddy_get_slot(PAGE_ZIP_MIN_SIZE));

	if (i < BUF_BUDDY_SIZES) {
		/* Try to allocate from the buddy system. */
		mutex_enter(&zip_free_mutex);
		block = buf_buddy_alloc_zip(i);

		if (block) {

			goto func_exit;
		}

		mutex_exit(&zip_free_mutex);
	}

	/* Try allocating from the buf_pool->free list. */
	block = buf_LRU_get_free_only();

	if (block) {

		goto alloc_big;
	}

	/* Try replacing an uncompressed page in the buffer pool. */
	//buf_pool_mutex_exit();
	mutex_exit(&LRU_list_mutex);
	if (have_page_hash_mutex) {
		rw_lock_x_unlock(&page_hash_latch);
	}
	block = buf_LRU_get_free_block();
	*lru = TRUE;
	//buf_pool_mutex_enter();
	mutex_enter(&LRU_list_mutex);
	if (have_page_hash_mutex) {
		rw_lock_x_lock(&page_hash_latch);
	}

alloc_big:
	buf_buddy_block_register(block);

	mutex_enter(&zip_free_mutex);
	block = buf_buddy_alloc_from(block->frame, i, BUF_BUDDY_SIZES);

func_exit:
	buf_buddy_stat[i].used++;
	mutex_exit(&zip_free_mutex);

	return(block);
}

/**********************************************************************//**
Try to relocate a block.
@return	TRUE if relocated */
static
ibool
buf_buddy_relocate(
/*===============*/
	void*	src,	/*!< in: block to relocate */
	void*	dst,	/*!< in: free block to relocate to */
	ulint	i,	/*!< in: index of buf_pool->zip_free[] */
	ibool	have_page_hash_mutex)
{
	buf_page_t*	bpage;
	const ulint	size	= BUF_BUDDY_LOW << i;
	ullint		usec	= ut_time_us(NULL);
	mutex_t*	mutex;
	ulint		space;
	ulint		page_no;

	//ut_ad(buf_pool_mutex_own());
	ut_ad(mutex_own(&zip_free_mutex));
	ut_ad(!mutex_own(&buf_pool_zip_mutex));
	ut_ad(!ut_align_offset(src, size));
	ut_ad(!ut_align_offset(dst, size));
	ut_ad(i >= buf_buddy_get_slot(PAGE_ZIP_MIN_SIZE));
	UNIV_MEM_ASSERT_W(dst, size);

	if (!have_page_hash_mutex) {
		mutex_exit(&zip_free_mutex);
		mutex_enter(&LRU_list_mutex);
		rw_lock_x_lock(&page_hash_latch);
	}

	/* We assume that all memory from buf_buddy_alloc()
	is used for compressed page frames. */

	/* We look inside the allocated objects returned by
	buf_buddy_alloc() and assume that each block is a compressed
	page that contains a valid space_id and page_no in the page
	header. Should the fields be invalid, we will be unable to
	relocate the block. */

	/* The src block may be split into smaller blocks,
	some of which may be free.  Thus, the
	mach_read_from_4() calls below may attempt to read
	from free memory.  The memory is "owned" by the buddy
	allocator (and it has been allocated from the buffer
	pool), so there is nothing wrong about this.  The
	mach_read_from_4() calls here will only trigger bogus
	Valgrind memcheck warnings in UNIV_DEBUG_VALGRIND builds. */
	space	= mach_read_from_4((const byte *) src
			+ FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
	page_no	= mach_read_from_4((const byte *) src
			+ FIL_PAGE_OFFSET);
	/* Suppress Valgrind warnings about conditional jump
	on uninitialized value. */
	UNIV_MEM_VALID(&space, sizeof space);
	UNIV_MEM_VALID(&page_no, sizeof page_no);
	bpage = buf_page_hash_get(space, page_no);

	if (!bpage || bpage->zip.data != src) {
		/* The block has probably been freshly
		allocated by buf_LRU_get_free_block() but not
		added to buf_pool->page_hash yet.  Obviously,
		it cannot be relocated. */

		if (!have_page_hash_mutex) {
			mutex_enter(&zip_free_mutex);
			mutex_exit(&LRU_list_mutex);
			rw_lock_x_unlock(&page_hash_latch);
		}
		return(FALSE);
	}

	if (page_zip_get_size(&bpage->zip) != size) {
		/* The block is of different size.  We would
		have to relocate all blocks covered by src.
		For the sake of simplicity, give up. */
		ut_ad(page_zip_get_size(&bpage->zip) < size);

		if (!have_page_hash_mutex) {
			mutex_enter(&zip_free_mutex);
			mutex_exit(&LRU_list_mutex);
			rw_lock_x_unlock(&page_hash_latch);
		}
		return(FALSE);
	}

	/* To keep latch order */
	if (have_page_hash_mutex)
		mutex_exit(&zip_free_mutex);

	/* The block must have been allocated, but it may
	contain uninitialized data. */
	UNIV_MEM_ASSERT_W(src, size);

	mutex = buf_page_get_mutex_enter(bpage);

	mutex_enter(&zip_free_mutex);

	if (mutex && buf_page_can_relocate(bpage)) {
		/* Relocate the compressed page. */
		ut_a(bpage->zip.data == src);
		memcpy(dst, src, size);
		bpage->zip.data = dst;
		mutex_exit(mutex);
		UNIV_MEM_INVALID(src, size);
		{
			buf_buddy_stat_t*	buddy_stat
				= &buf_buddy_stat[i];
			buddy_stat->relocated++;
			buddy_stat->relocated_usec
				+= ut_time_us(NULL) - usec;
		}

		if (!have_page_hash_mutex) {
			mutex_exit(&LRU_list_mutex);
			rw_lock_x_unlock(&page_hash_latch);
		}
		return(TRUE);
	}

	if (!have_page_hash_mutex) {
		mutex_exit(&LRU_list_mutex);
		rw_lock_x_unlock(&page_hash_latch);
	}

	if (mutex) {
		mutex_exit(mutex);
	}

	return(FALSE);
}

/**********************************************************************//**
Deallocate a block. */
UNIV_INTERN
void
buf_buddy_free_low(
/*===============*/
	void*	buf,	/*!< in: block to be freed, must not be
			pointed to by the buffer pool */
	ulint	i,	/*!< in: index of buf_pool->zip_free[],
			or BUF_BUDDY_SIZES */
	ibool	have_page_hash_mutex)
{
	buf_page_t*	bpage;
	buf_page_t*	buddy;

	//ut_ad(buf_pool_mutex_own());
	ut_ad(mutex_own(&zip_free_mutex));
	ut_ad(!mutex_own(&buf_pool_zip_mutex));
	ut_ad(i <= BUF_BUDDY_SIZES);
	ut_ad(i >= buf_buddy_get_slot(PAGE_ZIP_MIN_SIZE));
	ut_ad(buf_buddy_stat[i].used > 0);

	buf_buddy_stat[i].used--;

recombine:
	UNIV_MEM_ASSERT_AND_ALLOC(buf, BUF_BUDDY_LOW << i);
	((buf_page_t*) buf)->state = BUF_BLOCK_ZIP_FREE;

	if (i == BUF_BUDDY_SIZES) {
		mutex_exit(&zip_free_mutex);
		buf_buddy_block_free(buf, have_page_hash_mutex);
		mutex_enter(&zip_free_mutex);
		return;
	}

	ut_ad(i < BUF_BUDDY_SIZES);
	ut_ad(buf == ut_align_down(buf, BUF_BUDDY_LOW << i));
	ut_ad(!buf_pool_contains_zip(buf));

	/* Do not recombine blocks if there are few free blocks.
	We may waste up to 15360*max_len bytes to free blocks
	(1024 + 2048 + 4096 + 8192 = 15360) */
	if (UT_LIST_GET_LEN(buf_pool->zip_free[i]) < 16) {
		goto func_exit;
	}

	/* Try to combine adjacent blocks. */
	buddy = (buf_page_t*) buf_buddy_get(((byte*) buf), BUF_BUDDY_LOW << i);

#ifndef UNIV_DEBUG_VALGRIND
	/* When Valgrind instrumentation is not enabled, we can read
	buddy->state to quickly determine that a block is not free.
	When the block is not free, buddy->state belongs to a compressed
	page frame that may be flagged uninitialized in our Valgrind
	instrumentation.  */

	if (buddy->state != BUF_BLOCK_ZIP_FREE) {

		goto buddy_nonfree;
	}
#endif /* !UNIV_DEBUG_VALGRIND */

	for (bpage = UT_LIST_GET_FIRST(buf_pool->zip_free[i]); bpage; ) {
		ut_ad(buf_page_get_state(bpage) == BUF_BLOCK_ZIP_FREE);

		if (bpage == buddy) {
			/* The buddy is free: recombine */
			buf_buddy_remove_from_free(bpage, i);
buddy_is_free:
			ut_ad(buf_page_get_state(buddy) == BUF_BLOCK_ZIP_FREE);
			ut_ad(!buf_pool_contains_zip(buddy));
			i++;
			buf = ut_align_down(buf, BUF_BUDDY_LOW << i);

			goto recombine;
		}

		ut_a(bpage != buf);
		UNIV_MEM_ASSERT_W(bpage, BUF_BUDDY_LOW << i);
		bpage = UT_LIST_GET_NEXT(zip_list, bpage);
	}

#ifndef UNIV_DEBUG_VALGRIND
buddy_nonfree:
#endif /* !UNIV_DEBUG_VALGRIND */

	ut_d(BUF_BUDDY_LIST_VALIDATE(i));

	/* The buddy is not free. Is there a free block of this size? */
	bpage = UT_LIST_GET_LAST(buf_pool->zip_free[i]);

	if (bpage) {

		/* Remove the block from the free list, because a successful
		buf_buddy_relocate() will overwrite bpage->list. */
		buf_buddy_remove_from_free(bpage, i);

		/* Try to relocate the buddy of buf to the free block. */
		if (buf_buddy_relocate(buddy, bpage, i, have_page_hash_mutex)) {

			buddy->state = BUF_BLOCK_ZIP_FREE;
			goto buddy_is_free;
		}

		buf_buddy_add_to_free(bpage, i);
	}

func_exit:
	/* Free the block to the buddy list. */
	bpage = buf;

	/* Fill large blocks with a constant pattern. */
	ut_d(memset(bpage, i, BUF_BUDDY_LOW << i));
	UNIV_MEM_INVALID(bpage, BUF_BUDDY_LOW << i);

	bpage->state = BUF_BLOCK_ZIP_FREE;
	buf_buddy_add_to_free(bpage, i);
}