buf0buddy.cc File Reference

#include "buf0buddy.h"
#include "buf0buf.h"
#include "buf0lru.h"
#include "buf0flu.h"
#include "page0zip.h"
#include "srv0start.h"

Include dependency graph for buf0buddy.cc:

Go to the source code of this file.

Classes
struct	CheckZipFree

Macros
#define	THIS_MODULE
#define	BUF_BUDDY_STAMP_OFFSET   FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID
#define	BUF_BUDDY_STAMP_FREE   (SRV_LOG_SPACE_FIRST_ID)
#define	BUF_BUDDY_STAMP_NONFREE   (0XFFFFFFFF)
#define	buf_buddy_mem_invalid(buf, i)   ut_ad((i) <= BUF_BUDDY_SIZES)
#define	buf_buddy_stamp_nonfree(buf, i)
#define	BUF_BUDDY_LIST_VALIDATE(bp, i)

Enumerations
enum	buf_buddy_state_t { BUF_BUDDY_STATE_FREE, BUF_BUDDY_STATE_USED, BUF_BUDDY_STATE_PARTIALLY_USED }

Functions
UNIV_INLINE	__attribute__ ((warn_unused_result)) bool buf_buddy_stamp_is_free(const buf_buddy_free_t *buf)
UNIV_INLINE void	buf_buddy_stamp_free (buf_buddy_free_t *buf, ulint i)
UNIV_INLINE void *	buf_buddy_get (byte *page, ulint size)

Detailed Description

Binary buddy allocator for compressed pages

Created December 2006 by Marko Makela

Definition in file buf0buddy.cc.

Macro Definition Documentation

#define BUF_BUDDY_LIST_VALIDATE	(		bp,
			i
	)

Value:

UT_LIST_VALIDATE(list, buf_buddy_free_t,                \
                         bp->zip_free[i], CheckZipFree(i))

Definition at line 189 of file buf0buddy.cc.

#define BUF_BUDDY_STAMP_FREE   (SRV_LOG_SPACE_FIRST_ID)

Value that we stamp on all buffers that are currently on the zip_free

list. This value is stamped at BUF_BUDDY_STAMP_OFFSET offset

Definition at line 74 of file buf0buddy.cc.

#define BUF_BUDDY_STAMP_NONFREE   (0XFFFFFFFF)

Stamp value for non-free buffers. Will be overwritten by a non-zero

value by the consumer of the block

Definition at line 78 of file buf0buddy.cc.

#define buf_buddy_stamp_nonfree	(		buf,
			i
	)

Value:

do {                            \
        buf_buddy_mem_invalid(buf, i);                                  \
        memset(buf->stamp.bytes + BUF_BUDDY_STAMP_OFFSET, 0xff, 4);     \
} while (0)

Stamps a buddy nonfree.

Parameters

	in/out]	buf block to stamp
[in]	i	block size

Definition at line 145 of file buf0buddy.cc.

#define BUF_BUDDY_STAMP_OFFSET   FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID

When freeing a buf we attempt to coalesce by looking at its buddy

and deciding whether it is free or not. To ascertain if the buddy is free we look for BUF_BUDDY_STAMP_FREE at BUF_BUDDY_STAMP_OFFSET within the buddy. The question is how we can be sure that it is safe to look at BUF_BUDDY_STAMP_OFFSET. The answer lies in following invariants: All blocks allocated by buddy allocator are used for compressed page frame. A compressed table always have space_id < SRV_LOG_SPACE_FIRST_ID BUF_BUDDY_STAMP_OFFSET always points to the space_id field in a frame. – The above is true because we look at these fields when the corresponding buddy block is free which implies that: The block we are looking at must have an address aligned at the same size that its free buddy has. For example, if we have a free block of 8K then its buddy's address must be aligned at 8K as well. It is possible that the block we are looking at may have been further divided into smaller sized blocks but its starting address must still remain the start of a page frame i.e.: it cannot be middle of a block. For example, if we have a free block of size 8K then its buddy may be divided into blocks of, say, 1K, 1K, 2K, 4K but the buddy's address will still be the starting address of first 1K compressed page. What is important to note is that for any given block, the buddy's address cannot be in the middle of a larger block i.e.: in above example, our 8K block cannot have a buddy whose address is aligned on 8K but it is part of a larger 16K block. Offset within buf_buddy_free_t where free or non_free stamps are written.

Definition at line 70 of file buf0buddy.cc.

Enumeration Type Documentation

enum buf_buddy_state_t

Return type of buf_buddy_is_free()

Enumerator:

BUF_BUDDY_STATE_FREE	If the buddy to completely free
BUF_BUDDY_STATE_USED	Buddy currently in used
BUF_BUDDY_STATE_PARTIALLY_USED	Some sub-blocks in the buddy are in use

Definition at line 85 of file buf0buddy.cc.

Function Documentation

UNIV_INLINE __attribute__

(

(warn_unused_result)

)

const

Check if a buddy is stamped free.

Returns

whether the buddy is free

< in: block to check

Checks if a buf is free i.e.: in the zip_free[].

Return values

BUF_BUDDY_STATE_FREE	if fully free
BUF_BUDDY_STATE_USED	if currently in use
BUF_BUDDY_STATE_PARTIALLY_USED	if partially in use.

Definition at line 115 of file buf0buddy.cc.

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UNIV_INLINE void* buf_buddy_get	(	byte *	page,
		ulint	size
	)

Get the offset of the buddy of a compressed page frame.

Returns

the buddy relative of page

Parameters

page	in: compressed page
size	in: page size in bytes

Definition at line 158 of file buf0buddy.cc.

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UNIV_INLINE void buf_buddy_stamp_free	(	buf_buddy_free_t *	buf,
		ulint	i
	)

Stamps a buddy free.

Parameters

buf	in/out: block to stamp
i	in: block size

Definition at line 129 of file buf0buddy.cc.

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