/***************************************************************//**
Initializes a buffer to a random combination of hex DE and AD.
Used to erase freed memory. */
UNIV_INTERN
void
mem_erase_buf(
/*==========*/
byte* buf, /*!< in: pointer to buffer */
ulint n) /*!< in: length of buffer */
{
byte* ptr;
UNIV_MEM_ASSERT_W(buf, n);
for (ptr = buf; ptr < buf + n; ptr++) {
if (ut_rnd_gen_ibool()) {
*ptr = 0xDE;
} else {
*ptr = 0xAD;
}
}
UNIV_MEM_FREE(buf, n);
}
/**********************************************************************//**
Deallocate a block. */
UNIV_INTERN
void
buf_buddy_free_low(
/*===============*/
buf_pool_t* buf_pool, /*!< in: buffer pool instance */
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 */
{
buf_page_t* bpage;
buf_page_t* buddy;
ut_ad(buf_pool_mutex_own(buf_pool));
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_pool->buddy_stat[i].used > 0);
buf_pool->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) {
buf_buddy_block_free(buf_pool, buf);
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_pool, 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(buf_pool, bpage, i);
buddy_is_free:
ut_ad(buf_page_get_state(buddy) == BUF_BLOCK_ZIP_FREE);
ut_ad(!buf_pool_contains_zip(buf_pool, 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(list, bpage);
}
#ifndef UNIV_DEBUG_VALGRIND
buddy_nonfree:
#endif /* !UNIV_DEBUG_VALGRIND */
ut_d(BUF_BUDDY_LIST_VALIDATE(buf_pool, i));
/* The buddy is not free. Is there a free block of this size? */
bpage = UT_LIST_GET_FIRST(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(buf_pool, bpage, i);
/* Try to relocate the buddy of buf to the free block. */
if (buf_buddy_relocate(buf_pool, buddy, bpage, i)) {
buddy->state = BUF_BLOCK_ZIP_FREE;
goto buddy_is_free;
}
buf_buddy_add_to_free(buf_pool, 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(buf_pool, bpage, i);
}
/**********************************************************************//**
Try to relocate a block.
@return TRUE if relocated */
static
ibool
buf_buddy_relocate(
/*===============*/
buf_pool_t* buf_pool, /*!< in: buffer pool instance */
void* src, /*!< in: block to relocate */
void* dst, /*!< in: free block to relocate to */
ulint i) /*!< in: index of
buf_pool->zip_free[] */
{
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(buf_pool));
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);
/* 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(buf_pool, 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. */
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);
return(FALSE);
}
/* The block must have been allocated, but it may
contain uninitialized data. */
UNIV_MEM_ASSERT_W(src, size);
mutex = buf_page_get_mutex(bpage);
mutex_enter(mutex);
if (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_pool->buddy_stat[i];
buddy_stat->relocated++;
buddy_stat->relocated_usec
+= ut_time_us(NULL) - usec;
}
return(TRUE);
}
mutex_exit(mutex);
return(FALSE);
}
