/********************************************************************//**
High-level function which reads a page asynchronously from a file to the
buffer buf_pool if it is not already there. Sets the io_fix flag and sets
an exclusive lock on the buffer frame. The flag is cleared and the x-lock
released by the i/o-handler thread.
@return TRUE if page has been read in, FALSE in case of failure */
UNIV_INTERN
ibool
buf_read_page(
/*==========*/
ulint space, /*!< in: space id */
ulint zip_size,/*!< in: compressed page size in bytes, or 0 */
ulint offset, /*!< in: page number */
trx_t* trx)
{
buf_pool_t* buf_pool = buf_pool_get(space, offset);
ib_int64_t tablespace_version;
ulint count;
ulint err;
tablespace_version = fil_space_get_version(space);
/* We do the i/o in the synchronous aio mode to save thread
switches: hence TRUE */
count = buf_read_page_low(&err, TRUE, BUF_READ_ANY_PAGE, space,
zip_size, FALSE,
tablespace_version, offset, trx);
srv_buf_pool_reads += count;
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Error: trying to access"
" tablespace %lu page no. %lu,\n"
"InnoDB: but the tablespace does not exist"
" or is just being dropped.\n",
(ulong) space, (ulong) offset);
}
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin(buf_pool, TRUE);
/* Increment number of I/O operations used for LRU policy. */
buf_LRU_stat_inc_io();
return(count > 0);
}
/************************************************************************
High-level function which reads a page asynchronously from a file to the
buffer buf_pool if it is not already there. Sets the io_fix flag and sets
an exclusive lock on the buffer frame. The flag is cleared and the x-lock
released by the i/o-handler thread. Does a random read-ahead if it seems
sensible. */
ibool
buf_read_page(
/*==========*/
/* out: TRUE if success, FALSE otherwise */
ulint space, /* in: space id */
ulint offset) /* in: page number */
{
ib_longlong tablespace_version;
ulint count;
ulint err;
tablespace_version = fil_space_get_version(space);
buf_read_ahead_random(space, offset);
/* We do the i/o in the synchronous aio mode to save thread
switches: hence TRUE */
count = buf_read_page_low(&err, TRUE, BUF_READ_ANY_PAGE, space,
tablespace_version, offset);
srv_buf_pool_reads+= count;
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Error: trying to access"
" tablespace %lu page no. %lu,\n"
"InnoDB: but the tablespace does not exist"
" or is just being dropped.\n",
(ulong) space, (ulong) offset);
}
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin();
return(count > 0);
}
/********************************************************************//**
Issues read requests for pages which recovery wants to read in. */
UNIV_INTERN
void
buf_read_recv_pages(
/*================*/
ibool sync, /*!< in: TRUE if the caller
wants this function to wait
for the highest address page
to get read in, before this
function returns */
ulint space, /*!< in: space id */
ulint zip_size, /*!< in: compressed page size in
bytes, or 0 */
const ulint* page_nos, /*!< in: array of page numbers
to read, with the highest page
number the last in the
array */
ulint n_stored) /*!< in: number of page numbers
in the array */
{
ib_int64_t tablespace_version;
ulint count;
ulint err;
ulint i;
zip_size = fil_space_get_zip_size(space);
if (UNIV_UNLIKELY(zip_size == ULINT_UNDEFINED)) {
/* It is a single table tablespace and the .ibd file is
missing: do nothing */
/* the log records should be treated here same reason
for http://bugs.mysql.com/bug.php?id=43948 */
if (recv_recovery_is_on()) {
recv_addr_t* recv_addr;
mutex_enter(&(recv_sys->mutex));
if (recv_sys->apply_log_recs == FALSE) {
mutex_exit(&(recv_sys->mutex));
goto not_to_recover;
}
for (i = 0; i < n_stored; i++) {
/* recv_get_fil_addr_struct() */
recv_addr = HASH_GET_FIRST(recv_sys->addr_hash,
hash_calc_hash(ut_fold_ulint_pair(space, page_nos[i]),
recv_sys->addr_hash));
while (recv_addr) {
if ((recv_addr->space == space)
&& (recv_addr->page_no == page_nos[i])) {
break;
}
recv_addr = HASH_GET_NEXT(addr_hash, recv_addr);
}
if ((recv_addr == NULL)
|| (recv_addr->state == RECV_BEING_PROCESSED)
|| (recv_addr->state == RECV_PROCESSED)) {
continue;
}
recv_addr->state = RECV_PROCESSED;
ut_a(recv_sys->n_addrs);
recv_sys->n_addrs--;
}
mutex_exit(&(recv_sys->mutex));
fprintf(stderr, " (cannot find space: %lu)", space);
}
not_to_recover:
return;
}
tablespace_version = fil_space_get_version(space);
for (i = 0; i < n_stored; i++) {
buf_pool_t* buf_pool;
count = 0;
os_aio_print_debug = FALSE;
buf_pool = buf_pool_get(space, page_nos[i]);
while (buf_pool->n_pend_reads >= recv_n_pool_free_frames / 2) {
os_aio_simulated_wake_handler_threads();
os_thread_sleep(10000);
count++;
if (count > 1000) {
fprintf(stderr,
"InnoDB: Error: InnoDB has waited for"
" 10 seconds for pending\n"
"InnoDB: reads to the buffer pool to"
" be finished.\n"
"InnoDB: Number of pending reads %lu,"
" pending pread calls %lu\n",
(ulong) buf_pool->n_pend_reads,
(ulong)os_file_n_pending_preads);
os_aio_print_debug = TRUE;
}
}
os_aio_print_debug = FALSE;
if ((i + 1 == n_stored) && sync) {
buf_read_page_low(&err, TRUE, BUF_READ_ANY_PAGE, space,
zip_size, TRUE, tablespace_version,
page_nos[i], NULL);
} else {
buf_read_page_low(&err, FALSE, BUF_READ_ANY_PAGE
| OS_AIO_SIMULATED_WAKE_LATER,
space, zip_size, TRUE,
tablespace_version, page_nos[i], NULL);
}
}
os_aio_simulated_wake_handler_threads();
/* Flush pages from the end of all the LRU lists if necessary */
buf_flush_free_margins(FALSE);
#ifdef UNIV_DEBUG
if (buf_debug_prints) {
fprintf(stderr,
"Recovery applies read-ahead pages %lu\n",
(ulong) n_stored);
}
#endif /* UNIV_DEBUG */
}
/********************************************************************//**
Applies linear read-ahead if in the buf_pool the page is a border page of
a linear read-ahead area and all the pages in the area have been accessed.
Does not read any page if the read-ahead mechanism is not activated. Note
that the algorithm looks at the 'natural' adjacent successor and
predecessor of the page, which on the leaf level of a B-tree are the next
and previous page in the chain of leaves. To know these, the page specified
in (space, offset) must already be present in the buf_pool. Thus, the
natural way to use this function is to call it when a page in the buf_pool
is accessed the first time, calling this function just after it has been
bufferfixed.
NOTE 1: as this function looks at the natural predecessor and successor
fields on the page, what happens, if these are not initialized to any
sensible value? No problem, before applying read-ahead we check that the
area to read is within the span of the space, if not, read-ahead is not
applied. An uninitialized value may result in a useless read operation, but
only very improbably.
NOTE 2: the calling thread may own latches on pages: to avoid deadlocks this
function must be written such that it cannot end up waiting for these
latches!
NOTE 3: the calling thread must want access to the page given: this rule is
set to prevent unintended read-aheads performed by ibuf routines, a situation
which could result in a deadlock if the OS does not support asynchronous io.
@return number of page read requests issued */
UNIV_INTERN
ulint
buf_read_ahead_linear(
/*==================*/
ulint space, /*!< in: space id */
ulint zip_size, /*!< in: compressed page size in bytes, or 0 */
ulint offset, /*!< in: page number; see NOTE 3 above */
ibool inside_ibuf, /*!< in: TRUE if we are inside ibuf routine */
trx_t* trx)
{
buf_pool_t* buf_pool = buf_pool_get(space, offset);
ib_int64_t tablespace_version;
buf_page_t* bpage;
buf_frame_t* frame;
buf_page_t* pred_bpage = NULL;
ulint pred_offset;
ulint succ_offset;
ulint count;
int asc_or_desc;
ulint new_offset;
ulint fail_count;
ulint ibuf_mode;
ulint low, high;
ulint err;
ulint i;
const ulint buf_read_ahead_linear_area
= BUF_READ_AHEAD_AREA(buf_pool);
ulint threshold;
if (!(srv_read_ahead & 2)) {
return(0);
}
if (UNIV_UNLIKELY(srv_startup_is_before_trx_rollback_phase)) {
/* No read-ahead to avoid thread deadlocks */
return(0);
}
low = (offset / buf_read_ahead_linear_area)
* buf_read_ahead_linear_area;
high = (offset / buf_read_ahead_linear_area + 1)
* buf_read_ahead_linear_area;
if ((offset != low) && (offset != high - 1)) {
/* This is not a border page of the area: return */
return(0);
}
if (ibuf_bitmap_page(zip_size, offset)
|| trx_sys_hdr_page(space, offset)) {
/* If it is an ibuf bitmap page or trx sys hdr, we do
no read-ahead, as that could break the ibuf page access
order */
return(0);
}
/* Remember the tablespace version before we ask te tablespace size
below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
do not try to read outside the bounds of the tablespace! */
tablespace_version = fil_space_get_version(space);
buf_pool_mutex_enter(buf_pool);
if (high > fil_space_get_size(space)) {
buf_pool_mutex_exit(buf_pool);
/* The area is not whole, return */
return(0);
}
if (buf_pool->n_pend_reads
> buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
buf_pool_mutex_exit(buf_pool);
return(0);
}
buf_pool_mutex_exit(buf_pool);
/* Check that almost all pages in the area have been accessed; if
offset == low, the accesses must be in a descending order, otherwise,
in an ascending order. */
asc_or_desc = 1;
if (offset == low) {
asc_or_desc = -1;
}
/* How many out of order accessed pages can we ignore
when working out the access pattern for linear readahead */
threshold = ut_min((64 - srv_read_ahead_threshold),
BUF_READ_AHEAD_AREA(buf_pool));
fail_count = 0;
rw_lock_s_lock(&buf_pool->page_hash_latch);
for (i = low; i < high; i++) {
bpage = buf_page_hash_get(buf_pool, space, i);
if (bpage == NULL || !buf_page_is_accessed(bpage)) {
/* Not accessed */
fail_count++;
} else if (pred_bpage) {
/* Note that buf_page_is_accessed() returns
the time of the first access. If some blocks
of the extent existed in the buffer pool at
the time of a linear access pattern, the first
access times may be nonmonotonic, even though
the latest access times were linear. The
threshold (srv_read_ahead_factor) should help
a little against this. */
int res = ut_ulint_cmp(
buf_page_is_accessed(bpage),
buf_page_is_accessed(pred_bpage));
/* Accesses not in the right order */
if (res != 0 && res != asc_or_desc) {
fail_count++;
}
}
if (fail_count > threshold) {
/* Too many failures: return */
//buf_pool_mutex_exit(buf_pool);
rw_lock_s_unlock(&buf_pool->page_hash_latch);
return(0);
}
if (bpage && buf_page_is_accessed(bpage)) {
pred_bpage = bpage;
}
}
/* If we got this far, we know that enough pages in the area have
been accessed in the right order: linear read-ahead can be sensible */
bpage = buf_page_hash_get(buf_pool, space, offset);
if (bpage == NULL) {
//buf_pool_mutex_exit(buf_pool);
rw_lock_s_unlock(&buf_pool->page_hash_latch);
return(0);
}
switch (buf_page_get_state(bpage)) {
case BUF_BLOCK_ZIP_PAGE:
frame = bpage->zip.data;
break;
case BUF_BLOCK_FILE_PAGE:
frame = ((buf_block_t*) bpage)->frame;
break;
default:
ut_error;
break;
}
/* Read the natural predecessor and successor page addresses from
the page; NOTE that because the calling thread may have an x-latch
on the page, we do not acquire an s-latch on the page, this is to
prevent deadlocks. Even if we read values which are nonsense, the
algorithm will work. */
pred_offset = fil_page_get_prev(frame);
succ_offset = fil_page_get_next(frame);
//buf_pool_mutex_exit(buf_pool);
rw_lock_s_unlock(&buf_pool->page_hash_latch);
if ((offset == low) && (succ_offset == offset + 1)) {
/* This is ok, we can continue */
new_offset = pred_offset;
} else if ((offset == high - 1) && (pred_offset == offset - 1)) {
/* This is ok, we can continue */
new_offset = succ_offset;
} else {
/* Successor or predecessor not in the right order */
return(0);
}
low = (new_offset / buf_read_ahead_linear_area)
* buf_read_ahead_linear_area;
high = (new_offset / buf_read_ahead_linear_area + 1)
* buf_read_ahead_linear_area;
if ((new_offset != low) && (new_offset != high - 1)) {
/* This is not a border page of the area: return */
return(0);
}
if (high > fil_space_get_size(space)) {
/* The area is not whole, return */
return(0);
}
/* If we got this far, read-ahead can be sensible: do it */
ibuf_mode = inside_ibuf
? BUF_READ_IBUF_PAGES_ONLY | OS_AIO_SIMULATED_WAKE_LATER
: BUF_READ_ANY_PAGE | OS_AIO_SIMULATED_WAKE_LATER;
count = 0;
/* Since Windows XP seems to schedule the i/o handler thread
very eagerly, and consequently it does not wait for the
full read batch to be posted, we use special heuristics here */
os_aio_simulated_put_read_threads_to_sleep();
for (i = low; i < high; i++) {
/* It is only sensible to do read-ahead in the non-sync
aio mode: hence FALSE as the first parameter */
if (!ibuf_bitmap_page(zip_size, i)) {
count += buf_read_page_low(
&err, FALSE,
ibuf_mode,
space, zip_size, FALSE, tablespace_version, i, trx);
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Warning: in"
" linear readahead trying to access\n"
"InnoDB: tablespace %lu page %lu,\n"
"InnoDB: but the tablespace does not"
" exist or is just being dropped.\n",
(ulong) space, (ulong) i);
}
}
}
/* In simulated aio we wake the aio handler threads only after
queuing all aio requests, in native aio the following call does
nothing: */
os_aio_simulated_wake_handler_threads();
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin(buf_pool, TRUE);
#ifdef UNIV_DEBUG
if (buf_debug_prints && (count > 0)) {
fprintf(stderr,
"LINEAR read-ahead space %lu offset %lu pages %lu\n",
(ulong) space, (ulong) offset, (ulong) count);
}
#endif /* UNIV_DEBUG */
/* Read ahead is considered one I/O operation for the purpose of
LRU policy decision. */
buf_LRU_stat_inc_io();
buf_pool->stat.n_ra_pages_read += count;
return(count);
}
/********************************************************************//**
Applies a random read-ahead in buf_pool if there are at least a threshold
value of accessed pages from the random read-ahead area. Does not read any
page, not even the one at the position (space, offset), if the read-ahead
mechanism is not activated. NOTE 1: the calling thread may own latches on
pages: to avoid deadlocks this function must be written such that it cannot
end up waiting for these latches! NOTE 2: the calling thread must want
access to the page given: this rule is set to prevent unintended read-aheads
performed by ibuf routines, a situation which could result in a deadlock if
the OS does not support asynchronous i/o.
@return number of page read requests issued; NOTE that if we read ibuf
pages, it may happen that the page at the given page number does not
get read even if we return a positive value!
@return number of page read requests issued */
UNIV_INTERN
ulint
buf_read_ahead_random(
/*==================*/
ulint space, /*!< in: space id */
ulint zip_size, /*!< in: compressed page size in bytes,
or 0 */
ulint offset, /*!< in: page number of a page which
the current thread wants to access */
ibool inside_ibuf, /*!< in: TRUE if we are inside ibuf
routine */
trx_t* trx)
{
buf_pool_t* buf_pool = buf_pool_get(space, offset);
ib_int64_t tablespace_version;
ulint recent_blocks = 0;
ulint ibuf_mode;
ulint count;
ulint low, high;
ulint err;
ulint i;
const ulint buf_read_ahead_random_area
= BUF_READ_AHEAD_AREA(buf_pool);
if (!srv_random_read_ahead) {
/* Disabled by user */
return(0);
}
if (srv_startup_is_before_trx_rollback_phase) {
/* No read-ahead to avoid thread deadlocks */
return(0);
}
if (ibuf_bitmap_page(zip_size, offset)
|| trx_sys_hdr_page(space, offset)) {
/* If it is an ibuf bitmap page or trx sys hdr, we do
no read-ahead, as that could break the ibuf page access
order */
return(0);
}
/* Remember the tablespace version before we ask te tablespace size
below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
do not try to read outside the bounds of the tablespace! */
tablespace_version = fil_space_get_version(space);
low = (offset / buf_read_ahead_random_area)
* buf_read_ahead_random_area;
high = (offset / buf_read_ahead_random_area + 1)
* buf_read_ahead_random_area;
if (high > fil_space_get_size(space)) {
high = fil_space_get_size(space);
}
buf_pool_mutex_enter(buf_pool);
if (buf_pool->n_pend_reads
> buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
buf_pool_mutex_exit(buf_pool);
return(0);
}
/* Count how many blocks in the area have been recently accessed,
that is, reside near the start of the LRU list. */
for (i = low; i < high; i++) {
const buf_page_t* bpage =
buf_page_hash_get(buf_pool, space, i);
if (bpage
&& buf_page_is_accessed(bpage)
&& buf_page_peek_if_young(bpage)) {
recent_blocks++;
if (recent_blocks
>= BUF_READ_AHEAD_RANDOM_THRESHOLD(buf_pool)) {
buf_pool_mutex_exit(buf_pool);
goto read_ahead;
}
}
}
buf_pool_mutex_exit(buf_pool);
/* Do nothing */
return(0);
read_ahead:
/* Read all the suitable blocks within the area */
if (inside_ibuf) {
ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
} else {
ibuf_mode = BUF_READ_ANY_PAGE;
}
count = 0;
for (i = low; i < high; i++) {
/* It is only sensible to do read-ahead in the non-sync aio
mode: hence FALSE as the first parameter */
if (!ibuf_bitmap_page(zip_size, i)) {
count += buf_read_page_low(
&err, FALSE,
ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
space, zip_size, FALSE,
tablespace_version, i, trx);
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Warning: in random"
" readahead trying to access\n"
"InnoDB: tablespace %lu page %lu,\n"
"InnoDB: but the tablespace does not"
" exist or is just being dropped.\n",
(ulong) space, (ulong) i);
}
}
}
/* In simulated aio we wake the aio handler threads only after
queuing all aio requests, in native aio the following call does
nothing: */
os_aio_simulated_wake_handler_threads();
#ifdef UNIV_DEBUG
if (buf_debug_prints && (count > 0)) {
fprintf(stderr,
"Random read-ahead space %lu offset %lu pages %lu\n",
(ulong) space, (ulong) offset,
(ulong) count);
}
#endif /* UNIV_DEBUG */
/* Read ahead is considered one I/O operation for the purpose of
LRU policy decision. */
buf_LRU_stat_inc_io();
buf_pool->stat.n_ra_pages_read_rnd += count;
srv_buf_pool_reads += count;
return(count);
}
/********************************************************************//**
Issues read requests for pages which recovery wants to read in. */
UNIV_INTERN
void
buf_read_recv_pages(
/*================*/
ibool sync, /*!< in: TRUE if the caller
wants this function to wait
for the highest address page
to get read in, before this
function returns */
ulint space, /*!< in: space id */
ulint zip_size, /*!< in: compressed page size in
bytes, or 0 */
const ulint* page_nos, /*!< in: array of page numbers
to read, with the highest page
number the last in the
array */
ulint n_stored) /*!< in: number of page numbers
in the array */
{
ib_int64_t tablespace_version;
ulint count;
ulint err;
ulint i;
zip_size = fil_space_get_zip_size(space);
if (UNIV_UNLIKELY(zip_size == ULINT_UNDEFINED)) {
/* It is a single table tablespace and the .ibd file is
missing: do nothing */
return;
}
tablespace_version = fil_space_get_version(space);
for (i = 0; i < n_stored; i++) {
buf_pool_t* buf_pool;
count = 0;
os_aio_print_debug = FALSE;
buf_pool = buf_pool_get(space, page_nos[i]);
while (buf_pool->n_pend_reads >= recv_n_pool_free_frames / 2) {
os_aio_simulated_wake_handler_threads();
os_thread_sleep(10000);
count++;
if (count > 1000) {
fprintf(stderr,
"InnoDB: Error: InnoDB has waited for"
" 10 seconds for pending\n"
"InnoDB: reads to the buffer pool to"
" be finished.\n"
"InnoDB: Number of pending reads %lu,"
" pending pread calls %lu\n",
(ulong) buf_pool->n_pend_reads,
(ulong)os_file_n_pending_preads);
os_aio_print_debug = TRUE;
}
}
os_aio_print_debug = FALSE;
if ((i + 1 == n_stored) && sync) {
buf_read_page_low(&err, TRUE, BUF_READ_ANY_PAGE, space,
zip_size, TRUE, tablespace_version,
page_nos[i]);
} else {
buf_read_page_low(&err, FALSE, BUF_READ_ANY_PAGE
| OS_AIO_SIMULATED_WAKE_LATER,
space, zip_size, TRUE,
tablespace_version, page_nos[i]);
}
}
os_aio_simulated_wake_handler_threads();
/* Flush pages from the end of all the LRU lists if necessary */
buf_flush_free_margins();
#ifdef UNIV_DEBUG
if (buf_debug_prints) {
fprintf(stderr,
"Recovery applies read-ahead pages %lu\n",
(ulong) n_stored);
}
#endif /* UNIV_DEBUG */
}
void
buf_read_recv_pages(
/*================*/
ibool sync, /* in: TRUE if the caller wants this function
to wait for the highest address page to get
read in, before this function returns */
ulint space, /* in: space id */
ulint* page_nos, /* in: array of page numbers to read, with the
highest page number the last in the array */
ulint n_stored) /* in: number of page numbers in the array */
{
ib_longlong tablespace_version;
ulint count;
ulint err;
ulint i;
tablespace_version = fil_space_get_version(space);
for (i = 0; i < n_stored; i++) {
count = 0;
os_aio_print_debug = FALSE;
while (buf_pool->n_pend_reads >= recv_n_pool_free_frames / 2) {
os_aio_simulated_wake_handler_threads();
os_thread_sleep(500000);
count++;
if (count > 100) {
fprintf(stderr,
"InnoDB: Error: InnoDB has waited for"
" 50 seconds for pending\n"
"InnoDB: reads to the buffer pool to"
" be finished.\n"
"InnoDB: Number of pending reads %lu,"
" pending pread calls %lu\n",
(ulong) buf_pool->n_pend_reads,
(ulong)os_file_n_pending_preads);
os_aio_print_debug = TRUE;
}
}
os_aio_print_debug = FALSE;
if ((i + 1 == n_stored) && sync) {
buf_read_page_low(&err, TRUE, BUF_READ_ANY_PAGE,
space, tablespace_version,
page_nos[i]);
} else {
buf_read_page_low(&err, FALSE, BUF_READ_ANY_PAGE
| OS_AIO_SIMULATED_WAKE_LATER,
space, tablespace_version,
page_nos[i]);
}
}
os_aio_simulated_wake_handler_threads();
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin();
#ifdef UNIV_DEBUG
if (buf_debug_prints) {
fprintf(stderr,
"Recovery applies read-ahead pages %lu\n",
(ulong) n_stored);
}
#endif /* UNIV_DEBUG */
}
ulint
buf_read_ahead_linear(
/*==================*/
/* out: number of page read requests issued */
ulint space, /* in: space id */
ulint offset) /* in: page number of a page; NOTE: the current thread
must want access to this page (see NOTE 3 above) */
{
ib_longlong tablespace_version;
buf_block_t* block;
buf_frame_t* frame;
buf_block_t* pred_block = NULL;
ulint pred_offset;
ulint succ_offset;
ulint count;
int asc_or_desc;
ulint new_offset;
ulint fail_count;
ulint ibuf_mode;
ulint low, high;
ulint err;
ulint i;
if (srv_startup_is_before_trx_rollback_phase) {
/* No read-ahead to avoid thread deadlocks */
return(0);
}
if (ibuf_bitmap_page(offset) || trx_sys_hdr_page(space, offset)) {
/* If it is an ibuf bitmap page or trx sys hdr, we do
no read-ahead, as that could break the ibuf page access
order */
return(0);
}
low = (offset / BUF_READ_AHEAD_LINEAR_AREA)
* BUF_READ_AHEAD_LINEAR_AREA;
high = (offset / BUF_READ_AHEAD_LINEAR_AREA + 1)
* BUF_READ_AHEAD_LINEAR_AREA;
if ((offset != low) && (offset != high - 1)) {
/* This is not a border page of the area: return */
return(0);
}
/* Remember the tablespace version before we ask te tablespace size
below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
do not try to read outside the bounds of the tablespace! */
tablespace_version = fil_space_get_version(space);
mutex_enter(&(buf_pool->mutex));
if (high > fil_space_get_size(space)) {
mutex_exit(&(buf_pool->mutex));
/* The area is not whole, return */
return(0);
}
if (buf_pool->n_pend_reads
> buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
mutex_exit(&(buf_pool->mutex));
return(0);
}
/* Check that almost all pages in the area have been accessed; if
offset == low, the accesses must be in a descending order, otherwise,
in an ascending order. */
asc_or_desc = 1;
if (offset == low) {
asc_or_desc = -1;
}
fail_count = 0;
for (i = low; i < high; i++) {
block = buf_page_hash_get(space, i);
if ((block == NULL) || !block->accessed) {
/* Not accessed */
fail_count++;
} else if (pred_block
&& (ut_ulint_cmp(block->LRU_position,
pred_block->LRU_position)
!= asc_or_desc)) {
/* Accesses not in the right order */
fail_count++;
pred_block = block;
}
}
if (fail_count > BUF_READ_AHEAD_LINEAR_AREA
- BUF_READ_AHEAD_LINEAR_THRESHOLD) {
/* Too many failures: return */
mutex_exit(&(buf_pool->mutex));
return(0);
}
/* If we got this far, we know that enough pages in the area have
been accessed in the right order: linear read-ahead can be sensible */
block = buf_page_hash_get(space, offset);
if (block == NULL) {
mutex_exit(&(buf_pool->mutex));
return(0);
}
frame = block->frame;
/* Read the natural predecessor and successor page addresses from
the page; NOTE that because the calling thread may have an x-latch
on the page, we do not acquire an s-latch on the page, this is to
prevent deadlocks. Even if we read values which are nonsense, the
algorithm will work. */
pred_offset = fil_page_get_prev(frame);
succ_offset = fil_page_get_next(frame);
mutex_exit(&(buf_pool->mutex));
if ((offset == low) && (succ_offset == offset + 1)) {
/* This is ok, we can continue */
new_offset = pred_offset;
} else if ((offset == high - 1) && (pred_offset == offset - 1)) {
/* This is ok, we can continue */
new_offset = succ_offset;
} else {
/* Successor or predecessor not in the right order */
return(0);
}
low = (new_offset / BUF_READ_AHEAD_LINEAR_AREA)
* BUF_READ_AHEAD_LINEAR_AREA;
high = (new_offset / BUF_READ_AHEAD_LINEAR_AREA + 1)
* BUF_READ_AHEAD_LINEAR_AREA;
if ((new_offset != low) && (new_offset != high - 1)) {
/* This is not a border page of the area: return */
return(0);
}
if (high > fil_space_get_size(space)) {
/* The area is not whole, return */
return(0);
}
/* If we got this far, read-ahead can be sensible: do it */
if (ibuf_inside()) {
ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
} else {
ibuf_mode = BUF_READ_ANY_PAGE;
}
count = 0;
/* Since Windows XP seems to schedule the i/o handler thread
very eagerly, and consequently it does not wait for the
full read batch to be posted, we use special heuristics here */
os_aio_simulated_put_read_threads_to_sleep();
for (i = low; i < high; i++) {
/* It is only sensible to do read-ahead in the non-sync
aio mode: hence FALSE as the first parameter */
if (!ibuf_bitmap_page(i)) {
count += buf_read_page_low(
&err, FALSE,
ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
space, tablespace_version, i);
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Warning: in"
" linear readahead trying to access\n"
"InnoDB: tablespace %lu page %lu,\n"
"InnoDB: but the tablespace does not"
" exist or is just being dropped.\n",
(ulong) space, (ulong) i);
}
}
}
/* In simulated aio we wake the aio handler threads only after
queuing all aio requests, in native aio the following call does
nothing: */
os_aio_simulated_wake_handler_threads();
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin();
#ifdef UNIV_DEBUG
if (buf_debug_prints && (count > 0)) {
fprintf(stderr,
"LINEAR read-ahead space %lu offset %lu pages %lu\n",
(ulong) space, (ulong) offset, (ulong) count);
}
#endif /* UNIV_DEBUG */
++srv_read_ahead_seq;
return(count);
}
/************************************************************************
Applies a random read-ahead in buf_pool if there are at least a threshold
value of accessed pages from the random read-ahead area. Does not read any
page, not even the one at the position (space, offset), if the read-ahead
mechanism is not activated. NOTE 1: the calling thread may own latches on
pages: to avoid deadlocks this function must be written such that it cannot
end up waiting for these latches! NOTE 2: the calling thread must want
access to the page given: this rule is set to prevent unintended read-aheads
performed by ibuf routines, a situation which could result in a deadlock if
the OS does not support asynchronous i/o. */
static
ulint
buf_read_ahead_random(
/*==================*/
/* out: number of page read requests issued; NOTE
that if we read ibuf pages, it may happen that
the page at the given page number does not get
read even if we return a value > 0! */
ulint space, /* in: space id */
ulint offset) /* in: page number of a page which the current thread
wants to access */
{
ib_longlong tablespace_version;
buf_block_t* block;
ulint recent_blocks = 0;
ulint count;
ulint LRU_recent_limit;
ulint ibuf_mode;
ulint low, high;
ulint err;
ulint i;
if (srv_startup_is_before_trx_rollback_phase) {
/* No read-ahead to avoid thread deadlocks */
return(0);
}
if (ibuf_bitmap_page(offset) || trx_sys_hdr_page(space, offset)) {
/* If it is an ibuf bitmap page or trx sys hdr, we do
no read-ahead, as that could break the ibuf page access
order */
return(0);
}
/* Remember the tablespace version before we ask te tablespace size
below: if DISCARD + IMPORT changes the actual .ibd file meanwhile, we
do not try to read outside the bounds of the tablespace! */
tablespace_version = fil_space_get_version(space);
low = (offset / BUF_READ_AHEAD_RANDOM_AREA)
* BUF_READ_AHEAD_RANDOM_AREA;
high = (offset / BUF_READ_AHEAD_RANDOM_AREA + 1)
* BUF_READ_AHEAD_RANDOM_AREA;
if (high > fil_space_get_size(space)) {
high = fil_space_get_size(space);
}
/* Get the minimum LRU_position field value for an initial segment
of the LRU list, to determine which blocks have recently been added
to the start of the list. */
LRU_recent_limit = buf_LRU_get_recent_limit();
mutex_enter(&(buf_pool->mutex));
if (buf_pool->n_pend_reads
> buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
mutex_exit(&(buf_pool->mutex));
return(0);
}
/* Count how many blocks in the area have been recently accessed,
that is, reside near the start of the LRU list. */
for (i = low; i < high; i++) {
block = buf_page_hash_get(space, i);
if ((block)
&& (block->LRU_position > LRU_recent_limit)
&& block->accessed) {
recent_blocks++;
}
}
mutex_exit(&(buf_pool->mutex));
if (recent_blocks < BUF_READ_AHEAD_RANDOM_THRESHOLD) {
/* Do nothing */
return(0);
}
/* Read all the suitable blocks within the area */
if (ibuf_inside()) {
ibuf_mode = BUF_READ_IBUF_PAGES_ONLY;
} else {
ibuf_mode = BUF_READ_ANY_PAGE;
}
count = 0;
for (i = low; i < high; i++) {
/* It is only sensible to do read-ahead in the non-sync aio
mode: hence FALSE as the first parameter */
if (!ibuf_bitmap_page(i)) {
count += buf_read_page_low(
&err, FALSE,
ibuf_mode | OS_AIO_SIMULATED_WAKE_LATER,
space, tablespace_version, i);
if (err == DB_TABLESPACE_DELETED) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: Warning: in random"
" readahead trying to access\n"
"InnoDB: tablespace %lu page %lu,\n"
"InnoDB: but the tablespace does not"
" exist or is just being dropped.\n",
(ulong) space, (ulong) i);
}
}
}
/* In simulated aio we wake the aio handler threads only after
queuing all aio requests, in native aio the following call does
nothing: */
os_aio_simulated_wake_handler_threads();
#ifdef UNIV_DEBUG
if (buf_debug_prints && (count > 0)) {
fprintf(stderr,
"Random read-ahead space %lu offset %lu pages %lu\n",
(ulong) space, (ulong) offset,
(ulong) count);
}
#endif /* UNIV_DEBUG */
++srv_read_ahead_rnd;
return(count);
}
