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mariadb/storage/innobase/include/btr0pcur.ic
Marko Mäkelä 277ba134ad MDEV-26467: Avoid futile spin loops 
Typically, index_lock and fil_space_t::latch will be held for a longer
time than the spin loop in latch acquisition would be waiting for.
Let us avoid spin loops for those as well as dict_sys.latch, which
could be held in exclusive mode for a longer time (while loading
metadata into the buffer pool and the dictionary cache).

Performance testing on a dual Intel Xeon E5-2630 v4 (2 NUMA nodes)
suggests that the buffer pool page latch (block_lock) benefits from a
spin loop in both read-only and read-write workloads where the working
set is slightly larger than the buffer pool. Presumably, most contention
would occur on leaf page latches. Contention on upper level pages in
the buffer pool should intuitively last longer.

We introduce srw_spin_lock and srw_spin_mutex to allow users of
srw_lock or srw_mutex to opt in for the spin loop.
On Microsoft Windows, a spin loop variant was and will not be available;
srw_mutex and srw_lock will simply wrap SRWLOCK.
That is, on Microsoft Windows, the parameters innodb_sync_spin_loops
and innodb_spin_wait_delay will only affect block_lock.
2021-09-06 12:32:24 +03:00

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/*****************************************************************************
Copyright (c) 1996, 2015, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2015, 2021, MariaDB Corporation.
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.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
*****************************************************************************/
/**************************************************//**
@file include/btr0pcur.ic
The index tree persistent cursor
Created 2/23/1996 Heikki Tuuri
*******************************************************/
/*********************************************************//**
Gets the rel_pos field for a cursor whose position has been stored.
@return BTR_PCUR_ON, ... */
UNIV_INLINE
ulint
btr_pcur_get_rel_pos(
/*=================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor);
ut_ad(cursor->old_rec);
ut_ad(cursor->old_stored);
ut_ad(cursor->pos_state == BTR_PCUR_WAS_POSITIONED
|| cursor->pos_state == BTR_PCUR_IS_POSITIONED);
return(cursor->rel_pos);
}
#ifdef UNIV_DEBUG
/*********************************************************//**
Returns the btr cursor component of a persistent cursor.
@return pointer to btr cursor component */
UNIV_INLINE
btr_cur_t*
btr_pcur_get_btr_cur(
/*=================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
const btr_cur_t* btr_cur = &cursor->btr_cur;
return((btr_cur_t*) btr_cur);
}
/*********************************************************//**
Returns the page cursor component of a persistent cursor.
@return pointer to page cursor component */
UNIV_INLINE
page_cur_t*
btr_pcur_get_page_cur(
/*==================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
return(btr_cur_get_page_cur(btr_pcur_get_btr_cur(cursor)));
}
/*********************************************************//**
Returns the page of a persistent cursor.
@return pointer to the page */
UNIV_INLINE
page_t*
btr_pcur_get_page(
/*==============*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
return(btr_cur_get_page(btr_pcur_get_btr_cur(cursor)));
}
/*********************************************************//**
Returns the buffer block of a persistent cursor.
@return pointer to the block */
UNIV_INLINE
buf_block_t*
btr_pcur_get_block(
/*===============*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
return(btr_cur_get_block(btr_pcur_get_btr_cur(cursor)));
}
/*********************************************************//**
Returns the record of a persistent cursor.
@return pointer to the record */
UNIV_INLINE
rec_t*
btr_pcur_get_rec(
/*=============*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
return(btr_cur_get_rec(btr_pcur_get_btr_cur(cursor)));
}
#endif /* UNIV_DEBUG */
/**************************************************************//**
Gets the up_match value for a pcur after a search.
@return number of matched fields at the cursor or to the right if
search mode was PAGE_CUR_GE, otherwise undefined */
UNIV_INLINE
ulint
btr_pcur_get_up_match(
/*==================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
const btr_cur_t* btr_cursor;
ut_ad((cursor->pos_state == BTR_PCUR_WAS_POSITIONED)
|| (cursor->pos_state == BTR_PCUR_IS_POSITIONED));
btr_cursor = btr_pcur_get_btr_cur(cursor);
ut_ad(btr_cursor->up_match != ULINT_UNDEFINED);
return(btr_cursor->up_match);
}
/**************************************************************//**
Gets the low_match value for a pcur after a search.
@return number of matched fields at the cursor or to the right if
search mode was PAGE_CUR_LE, otherwise undefined */
UNIV_INLINE
ulint
btr_pcur_get_low_match(
/*===================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
const btr_cur_t* btr_cursor;
ut_ad((cursor->pos_state == BTR_PCUR_WAS_POSITIONED)
|| (cursor->pos_state == BTR_PCUR_IS_POSITIONED));
btr_cursor = btr_pcur_get_btr_cur(cursor);
ut_ad(btr_cursor->low_match != ULINT_UNDEFINED);
return(btr_cursor->low_match);
}
/*********************************************************//**
Checks if the persistent cursor is after the last user record on
a page. */
UNIV_INLINE
ibool
btr_pcur_is_after_last_on_page(
/*===========================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
return(page_cur_is_after_last(btr_pcur_get_page_cur(cursor)));
}
/*********************************************************//**
Checks if the persistent cursor is before the first user record on
a page. */
UNIV_INLINE
ibool
btr_pcur_is_before_first_on_page(
/*=============================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
return(page_cur_is_before_first(btr_pcur_get_page_cur(cursor)));
}
/*********************************************************//**
Checks if the persistent cursor is on a user record. */
UNIV_INLINE
ibool
btr_pcur_is_on_user_rec(
/*====================*/
const btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
if (btr_pcur_is_before_first_on_page(cursor)
|| btr_pcur_is_after_last_on_page(cursor)) {
return(FALSE);
}
return(TRUE);
}
/*********************************************************//**
Checks if the persistent cursor is before the first user record in
the index tree. */
static inline bool btr_pcur_is_before_first_in_tree(btr_pcur_t* cursor)
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
return !page_has_prev(btr_pcur_get_page(cursor))
&& page_cur_is_before_first(btr_pcur_get_page_cur(cursor));
}
/*********************************************************//**
Checks if the persistent cursor is after the last user record in
the index tree. */
static inline bool btr_pcur_is_after_last_in_tree(btr_pcur_t* cursor)
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
return !page_has_next(btr_pcur_get_page(cursor))
&& page_cur_is_after_last(btr_pcur_get_page_cur(cursor));
}
/*********************************************************//**
Moves the persistent cursor to the next record on the same page. */
UNIV_INLINE
void
btr_pcur_move_to_next_on_page(
/*==========================*/
btr_pcur_t* cursor) /*!< in/out: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
page_cur_move_to_next(btr_pcur_get_page_cur(cursor));
cursor->old_stored = false;
}
/*********************************************************//**
Moves the persistent cursor to the previous record on the same page. */
UNIV_INLINE
void
btr_pcur_move_to_prev_on_page(
/*==========================*/
btr_pcur_t* cursor) /*!< in/out: persistent cursor */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
page_cur_move_to_prev(btr_pcur_get_page_cur(cursor));
cursor->old_stored = false;
}
/*********************************************************//**
Moves the persistent cursor to the next user record in the tree. If no user
records are left, the cursor ends up 'after last in tree'.
@return TRUE if the cursor moved forward, ending on a user record */
UNIV_INLINE
ibool
btr_pcur_move_to_next_user_rec(
/*===========================*/
btr_pcur_t* cursor, /*!< in: persistent cursor; NOTE that the
function may release the page latch */
mtr_t* mtr) /*!< in: mtr */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
cursor->old_stored = false;
loop:
if (btr_pcur_is_after_last_on_page(cursor)) {
if (btr_pcur_is_after_last_in_tree(cursor)) {
return(FALSE);
}
btr_pcur_move_to_next_page(cursor, mtr);
} else {
btr_pcur_move_to_next_on_page(cursor);
}
if (btr_pcur_is_on_user_rec(cursor)) {
return(TRUE);
}
goto loop;
}
/*********************************************************//**
Moves the persistent cursor to the next record in the tree. If no records are
left, the cursor stays 'after last in tree'.
@return TRUE if the cursor was not after last in tree */
UNIV_INLINE
ibool
btr_pcur_move_to_next(
/*==================*/
btr_pcur_t* cursor, /*!< in: persistent cursor; NOTE that the
function may release the page latch */
mtr_t* mtr) /*!< in: mtr */
{
ut_ad(cursor->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
cursor->old_stored = false;
if (btr_pcur_is_after_last_on_page(cursor)) {
if (btr_pcur_is_after_last_in_tree(cursor)) {
return(FALSE);
}
btr_pcur_move_to_next_page(cursor, mtr);
return(TRUE);
}
btr_pcur_move_to_next_on_page(cursor);
return(TRUE);
}
/**************************************************************//**
Commits the mtr and sets the pcur latch mode to BTR_NO_LATCHES,
that is, the cursor becomes detached.
Function btr_pcur_store_position should be used before calling this,
if restoration of cursor is wanted later. */
UNIV_INLINE
void
btr_pcur_commit_specify_mtr(
/*========================*/
btr_pcur_t* pcur, /*!< in: persistent cursor */
mtr_t* mtr) /*!< in: mtr to commit */
{
ut_ad(pcur->pos_state == BTR_PCUR_IS_POSITIONED);
pcur->latch_mode = BTR_NO_LATCHES;
mtr_commit(mtr);
pcur->pos_state = BTR_PCUR_WAS_POSITIONED;
}
/** Commits the mtr and sets the clustered index pcur and secondary index
pcur latch mode to BTR_NO_LATCHES, that is, the cursor becomes detached.
Function btr_pcur_store_position should be used for both cursor before
calling this, if restoration of cursor is wanted later.
@param[in] pcur persistent cursor
@param[in] sec_pcur secondary index persistent cursor
@param[in] mtr mtr to commit */
UNIV_INLINE
void
btr_pcurs_commit_specify_mtr(
btr_pcur_t* pcur,
btr_pcur_t* sec_pcur,
mtr_t* mtr)
{
ut_ad(pcur->pos_state == BTR_PCUR_IS_POSITIONED);
ut_ad(sec_pcur->pos_state == BTR_PCUR_IS_POSITIONED);
pcur->latch_mode = BTR_NO_LATCHES;
sec_pcur->latch_mode = BTR_NO_LATCHES;
mtr_commit(mtr);
pcur->pos_state = BTR_PCUR_WAS_POSITIONED;
sec_pcur->pos_state = BTR_PCUR_WAS_POSITIONED;
}
/**************************************************************//**
Sets the old_rec_buf field to NULL. */
UNIV_INLINE
void
btr_pcur_init(
/*==========*/
btr_pcur_t* pcur) /*!< in: persistent cursor */
{
pcur->old_stored = false;
pcur->old_rec_buf = NULL;
pcur->old_rec = NULL;
pcur->btr_cur.rtr_info = NULL;
}
/** Free old_rec_buf.
@param[in] pcur Persistent cursor holding old_rec to be freed. */
UNIV_INLINE
void
btr_pcur_free(
btr_pcur_t* pcur)
{
ut_free(pcur->old_rec_buf);
}
/**************************************************************//**
Initializes and opens a persistent cursor to an index tree. It should be
closed with btr_pcur_close. */
UNIV_INLINE
dberr_t
btr_pcur_open_low(
/*==============*/
dict_index_t* index, /*!< in: index */
ulint level, /*!< in: level in the btree */
const dtuple_t* tuple, /*!< in: tuple on which search done */
page_cur_mode_t mode, /*!< in: PAGE_CUR_L, ...;
NOTE that if the search is made using a unique
prefix of a record, mode should be
PAGE_CUR_LE, not PAGE_CUR_GE, as the latter
may end up on the previous page from the
record! */
ulint latch_mode,/*!< in: BTR_SEARCH_LEAF, ... */
btr_pcur_t* cursor, /*!< in: memory buffer for persistent cursor */
ib_uint64_t autoinc,/*!< in: PAGE_ROOT_AUTO_INC to be written
(0 if none) */
mtr_t* mtr) /*!< in: mtr */
{
btr_cur_t* btr_cursor;
dberr_t err = DB_SUCCESS;
/* Initialize the cursor */
btr_pcur_init(cursor);
cursor->latch_mode = BTR_LATCH_MODE_WITHOUT_FLAGS(latch_mode);
cursor->search_mode = mode;
/* Search with the tree cursor */
btr_cursor = btr_pcur_get_btr_cur(cursor);
ut_ad(!dict_index_is_spatial(index));
err = btr_cur_search_to_nth_level_func(
index, level, tuple, mode, latch_mode, btr_cursor,
#ifdef BTR_CUR_HASH_ADAPT
NULL,
#endif /* BTR_CUR_HASH_ADAPT */
mtr, autoinc);
if (UNIV_UNLIKELY(err != DB_SUCCESS)) {
ib::warn() << "btr_pcur_open_low"
<< " level: " << level
<< " table: " << index->table->name
<< " index: " << index->name
<< " error: " << err;
}
cursor->pos_state = BTR_PCUR_IS_POSITIONED;
cursor->trx_if_known = NULL;
return(err);
}
/**************************************************************//**
Opens an persistent cursor to an index tree without initializing the
cursor. */
UNIV_INLINE
dberr_t
btr_pcur_open_with_no_init_func(
/*============================*/
dict_index_t* index, /*!< in: index */
const dtuple_t* tuple, /*!< in: tuple on which search done */
page_cur_mode_t mode, /*!< in: PAGE_CUR_L, ...;
NOTE that if the search is made using a unique
prefix of a record, mode should be
PAGE_CUR_LE, not PAGE_CUR_GE, as the latter
may end up on the previous page of the
record! */
ulint latch_mode,/*!< in: BTR_SEARCH_LEAF, ...;
NOTE that if ahi_latch then we might not
acquire a cursor page latch, but assume
that the ahi_latch protects the record! */
btr_pcur_t* cursor, /*!< in: memory buffer for persistent cursor */
#ifdef BTR_CUR_HASH_ADAPT
srw_spin_lock* ahi_latch,
/*!< in: currently held AHI rdlock, or NULL */
#endif /* BTR_CUR_HASH_ADAPT */
mtr_t* mtr) /*!< in: mtr */
{
btr_cur_t* btr_cursor;
dberr_t err = DB_SUCCESS;
cursor->latch_mode = BTR_LATCH_MODE_WITHOUT_INTENTION(latch_mode);
cursor->search_mode = mode;
/* Search with the tree cursor */
btr_cursor = btr_pcur_get_btr_cur(cursor);
err = btr_cur_search_to_nth_level_func(
index, 0, tuple, mode, latch_mode, btr_cursor,
#ifdef BTR_CUR_HASH_ADAPT
ahi_latch,
#endif /* BTR_CUR_HASH_ADAPT */
mtr);
cursor->pos_state = BTR_PCUR_IS_POSITIONED;
cursor->old_stored = false;
cursor->trx_if_known = NULL;
return err;
}
/*****************************************************************//**
Opens a persistent cursor at either end of an index. */
UNIV_INLINE
dberr_t
btr_pcur_open_at_index_side(
/*========================*/
bool from_left, /*!< in: true if open to the low end,
false if to the high end */
dict_index_t* index, /*!< in: index */
ulint latch_mode, /*!< in: latch mode */
btr_pcur_t* pcur, /*!< in/out: cursor */
bool init_pcur, /*!< in: whether to initialize pcur */
ulint level, /*!< in: level to search for
(0=leaf) */
mtr_t* mtr) /*!< in/out: mini-transaction */
{
dberr_t err = DB_SUCCESS;
pcur->latch_mode = BTR_LATCH_MODE_WITHOUT_FLAGS(latch_mode);
pcur->search_mode = from_left ? PAGE_CUR_G : PAGE_CUR_L;
if (init_pcur) {
btr_pcur_init(pcur);
}
err = btr_cur_open_at_index_side(
from_left, index, latch_mode,
btr_pcur_get_btr_cur(pcur), level, mtr);
pcur->pos_state = BTR_PCUR_IS_POSITIONED;
pcur->old_stored = false;
pcur->trx_if_known = NULL;
return (err);
}
/**********************************************************************//**
Positions a cursor at a randomly chosen position within a B-tree.
@return true if the index is available and we have put the cursor, false
if the index is unavailable */
UNIV_INLINE
bool
btr_pcur_open_at_rnd_pos(
dict_index_t* index, /*!< in: index */
ulint latch_mode, /*!< in: BTR_SEARCH_LEAF, ... */
btr_pcur_t* cursor, /*!< in/out: B-tree pcur */
mtr_t* mtr) /*!< in: mtr */
{
/* Initialize the cursor */
cursor->latch_mode = latch_mode;
cursor->search_mode = PAGE_CUR_G;
btr_pcur_init(cursor);
bool available;
available = btr_cur_open_at_rnd_pos(index, latch_mode,
btr_pcur_get_btr_cur(cursor),
mtr);
cursor->pos_state = BTR_PCUR_IS_POSITIONED;
cursor->old_stored = false;
cursor->trx_if_known = NULL;
return(available);
}
/**************************************************************//**
Frees the possible memory heap of a persistent cursor and sets the latch
mode of the persistent cursor to BTR_NO_LATCHES.
WARNING: this function does not release the latch on the page where the
cursor is currently positioned. The latch is acquired by the
"move to next/previous" family of functions. Since recursive shared locks
are not allowed, you must take care (if using the cursor in S-mode) to
manually release the latch by either calling
btr_leaf_page_release(btr_pcur_get_block(&pcur), pcur.latch_mode, mtr)
or by committing the mini-transaction right after btr_pcur_close().
A subsequent attempt to crawl the same page in the same mtr would cause
an assertion failure. */
UNIV_INLINE
void
btr_pcur_close(
/*===========*/
btr_pcur_t* cursor) /*!< in: persistent cursor */
{
ut_free(cursor->old_rec_buf);
if (cursor->btr_cur.rtr_info) {
rtr_clean_rtr_info(cursor->btr_cur.rtr_info, true);
cursor->btr_cur.rtr_info = NULL;
}
cursor->old_rec = NULL;
cursor->old_rec_buf = NULL;
cursor->btr_cur.page_cur.rec = NULL;
cursor->btr_cur.page_cur.block = NULL;
cursor->old_rec = NULL;
cursor->old_stored = false;
cursor->latch_mode = BTR_NO_LATCHES;
cursor->pos_state = BTR_PCUR_NOT_POSITIONED;
cursor->trx_if_known = NULL;
}
/*********************************************************//**
Moves the persistent cursor to the infimum record on the same page. */
UNIV_INLINE
void
btr_pcur_move_before_first_on_page(
/*===============================*/
btr_pcur_t* cursor) /*!< in/out: persistent cursor */
{
ut_ad(cursor->latch_mode != BTR_NO_LATCHES);
page_cur_set_before_first(btr_pcur_get_block(cursor),
btr_pcur_get_page_cur(cursor));
cursor->old_stored = false;
}
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