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Added Innobase to source distribution

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monty@donna.mysql.com
2001-02-17 14:19:19 +02:00
parent 024e2f39c9
commit c533308a15
421 changed files with 170195 additions and 969 deletions
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innobase/buf/buf0rea.c Normal file
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/******************************************************
The database buffer read
(c) 1995 Innobase Oy
Created 11/5/1995 Heikki Tuuri
*******************************************************/
#include "buf0rea.h"
#include "fil0fil.h"
#include "mtr0mtr.h"
#include "buf0buf.h"
#include "buf0flu.h"
#include "buf0lru.h"
#include "ibuf0ibuf.h"
#include "log0recv.h"
#include "trx0sys.h"
#include "os0file.h"
/* The size in blocks of the area where the random read-ahead algorithm counts
the accessed pages when deciding whether to read-ahead */
#define BUF_READ_AHEAD_RANDOM_AREA BUF_READ_AHEAD_AREA
/* There must be at least this many pages in buf_pool in the area to start
a random read-ahead */
#define BUF_READ_AHEAD_RANDOM_THRESHOLD (5 + BUF_READ_AHEAD_RANDOM_AREA / 8)
/* The linear read-ahead area size */
#define BUF_READ_AHEAD_LINEAR_AREA BUF_READ_AHEAD_AREA
/* The linear read-ahead threshold */
#define BUF_READ_AHEAD_LINEAR_THRESHOLD (3 * BUF_READ_AHEAD_LINEAR_AREA / 8)
/* If there are buf_pool->curr_size per the number below pending reads, then
read-ahead is not done: this is to prevent flooding the buffer pool with
i/o-fixed buffer blocks */
#define BUF_READ_AHEAD_PEND_LIMIT 2
/************************************************************************
Low-level function which reads a page asynchronously from a file to the
buffer buf_pool if it is not already there, in which case does nothing.
Sets the io_fix flag and sets an exclusive lock on the buffer frame. The
flag is cleared and the x-lock released by an i/o-handler thread. */
static
ulint
buf_read_page_low(
/*==============*/
/* out: 1 if a read request was queued, 0 if the page
already resided in buf_pool */
ibool sync, /* in: TRUE if synchronous aio is desired */
ulint mode, /* in: BUF_READ_IBUF_PAGES_ONLY, ...,
ORed to OS_AIO_SIMULATED_WAKE_LATER (see below
at read-ahead functions) */
ulint space, /* in: space id */
ulint offset) /* in: page number */
{
buf_block_t* block;
ulint wake_later;
wake_later = mode & OS_AIO_SIMULATED_WAKE_LATER;
mode = mode & ~OS_AIO_SIMULATED_WAKE_LATER;
#ifdef UNIV_LOG_DEBUG
if (space % 2 == 1) {
/* We are updating a replicate space while holding the
log mutex: the read must be handled before other reads
which might incur ibuf operations and thus write to the log */
printf("Log debug: reading replicate page in sync mode\n");
sync = TRUE;
}
#endif
if (trx_sys_hdr_page(space, offset)) {
/* Trx sys header is so low in the latching order that we play
safe and do not leave the i/o-completion to an asynchronous
i/o-thread: */
sync = TRUE;
}
block = buf_page_init_for_read(mode, space, offset);
if (block != NULL) {
fil_io(OS_FILE_READ | wake_later,
sync, space, offset, 0, UNIV_PAGE_SIZE,
(void*)block->frame, (void*)block);
if (sync) {
/* The i/o is already completed when we arrive from
fil_read */
buf_page_io_complete(block);
}
return(1);
}
return(0);
}
/************************************************************************
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 */
{
buf_block_t* block;
ulint recent_blocks = 0;
ulint count;
ulint LRU_recent_limit;
ulint ibuf_mode;
ulint low, high;
ulint i;
if (ibuf_bitmap_page(offset)) {
/* If it is an ibuf bitmap page, we do no read-ahead, as
that could break the ibuf page access order */
return(0);
}
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(FALSE, ibuf_mode
| OS_AIO_SIMULATED_WAKE_LATER,
space, 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();
if (buf_debug_prints && (count > 0)) {
printf("Random read-ahead space %lu offset %lu pages %lu\n",
space, offset, count);
}
return(count);
}
/************************************************************************
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. */
ulint
buf_read_page(
/*==========*/
/* out: number of page read requests issued: this can
be > 1 if read-ahead occurred */
ulint space, /* in: space id */
ulint offset) /* in: page number */
{
ulint count;
ulint count2;
count = buf_read_ahead_random(space, offset);
/* We do the i/o in the synchronous aio mode to save thread
switches: hence TRUE */
count2 = buf_read_page_low(TRUE, BUF_READ_ANY_PAGE, space, offset);
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin();
return(count + count2);
}
/************************************************************************
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 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. */
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) */
{
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 i;
if (ibuf_bitmap_page(offset)) {
/* If it is an ibuf bitmap page, 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);
}
if (high > fil_space_get_size(space)) {
/* The area is not whole, return */
return(0);
}
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);
}
/* 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;
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(FALSE, ibuf_mode
| OS_AIO_SIMULATED_WAKE_LATER,
space, 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();
if (buf_debug_prints && (count > 0)) {
printf(
"LINEAR read-ahead space %lu offset %lu pages %lu\n",
space, offset, count);
}
return(count);
}
/************************************************************************
Issues read requests for pages which the ibuf module wants to read in, in
order to contract insert buffer trees. Technically, this function is like
a read-ahead function. */
void
buf_read_ibuf_merge_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 */
{
ulint i;
ut_ad(!ibuf_inside());
#ifdef UNIV_IBUF_DEBUG
ut_a(n_stored < UNIV_PAGE_SIZE);
#endif
while (buf_pool->n_pend_reads >
buf_pool->curr_size / BUF_READ_AHEAD_PEND_LIMIT) {
os_thread_sleep(500000);
}
for (i = 0; i < n_stored; i++) {
if ((i + 1 == n_stored) && sync) {
buf_read_page_low(TRUE, BUF_READ_ANY_PAGE, space,
page_nos[i]);
} else {
buf_read_page_low(FALSE, BUF_READ_ANY_PAGE, space,
page_nos[i]);
}
}
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin();
if (buf_debug_prints) {
printf("Ibuf merge read-ahead space %lu pages %lu\n",
space, n_stored);
}
}
/************************************************************************
Issues read requests for pages which recovery wants to read in. */
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 */
{
ulint i;
for (i = 0; i < n_stored; i++) {
while (buf_pool->n_pend_reads >= RECV_POOL_N_FREE_BLOCKS / 2) {
os_aio_simulated_wake_handler_threads();
os_thread_sleep(500000);
}
if ((i + 1 == n_stored) && sync) {
buf_read_page_low(TRUE, BUF_READ_ANY_PAGE, space,
page_nos[i]);
} else {
buf_read_page_low(FALSE, BUF_READ_ANY_PAGE
| OS_AIO_SIMULATED_WAKE_LATER,
space, page_nos[i]);
}
}
os_aio_simulated_wake_handler_threads();
/* Flush pages from the end of the LRU list if necessary */
buf_flush_free_margin();
if (buf_debug_prints) {
printf("Recovery applies read-ahead pages %lu\n", n_stored);
}
}