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Commit 9fad661f authored by osku's avatar osku
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Forward port r121 from branches/5.0: 

Optimize sync array behavior by not having the woken threads reserve the
sync array mutex.
parent dd42a65a
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Showing with 115 additions and 50 deletions
include/sync0arr.h
View file @ 9fad661f
......@@ -66,12 +66,12 @@ sync_array_wait_event(
sync_array_t* arr, /* in: wait array */
ulint index); /* in: index of the reserved cell */
/**********************************************************************
Frees the cell. NOTE! sync_array_wait_event frees the cell
automatically! */
Frees the cell safely by reserving the sync array mutex and decrementing
n_reserved if necessary. Should only be called from mutex_spin_wait. */
void
sync_array_free_cell(
/*=================*/
sync_array_free_cell_protected(
/*===========================*/
sync_array_t* arr, /* in: wait array */
ulint index); /* in: index of the cell in array */
/**************************************************************************
......
sync/sync0arr.c
View file @ 9fad661f
......@@ -46,9 +46,18 @@ algorithm, because 10 000 events are created fast, but
until a resource is released. The suspending is implemented
using an operating system event semaphore. */
struct sync_cell_struct {
/* State of the cell. SC_WAKING_UP means
sync_array_struct->n_reserved has been decremented, but the thread
in this cell has not waken up yet. When it does, it will set the
state to SC_FREE. Note that this is done without the protection of
any mutex. */
enum { SC_FREE, SC_RESERVED, SC_WAKING_UP } state;
void* wait_object; /* pointer to the object the
thread is waiting for; if NULL
the cell is free for use */
thread is waiting for; like state,
this can change from non-NULL to
NULL without any mutex protection */
mutex_t* old_wait_mutex; /* the latest wait mutex in cell */
rw_lock_t* old_wait_rw_lock;/* the latest wait rw-lock in cell */
ulint request_type; /* lock type requested on the
......@@ -217,6 +226,7 @@ sync_array_create(
for (i = 0; i < n_cells; i++) {
cell = sync_array_get_nth_cell(arr, i);
cell->state = SC_FREE;
cell->wait_object = NULL;
/* Create an operating system event semaphore with no name */
......@@ -282,7 +292,7 @@ sync_array_validate(
for (i = 0; i < arr->n_cells; i++) {
cell = sync_array_get_nth_cell(arr, i);
if (cell->wait_object != NULL) {
if (cell->state == SC_RESERVED) {
count++;
}
}
......@@ -293,13 +303,14 @@ sync_array_validate(
}
/***********************************************************************
Puts the cell event in set state. */
Puts the cell event in set state. Sync array mutex has to be reserved. */
static
void
sync_cell_event_set(
/*================*/
sync_cell_t* cell) /* in: array cell */
{
cell->state = SC_WAKING_UP;
os_event_set(cell->event);
cell->event_set = TRUE;
}
......@@ -344,13 +355,14 @@ sync_array_reserve_cell(
for (i = 0; i < arr->n_cells; i++) {
cell = sync_array_get_nth_cell(arr, i);
if (cell->wait_object == NULL) {
if (cell->state == SC_FREE) {
/* Make sure the event is reset */
if (cell->event_set) {
sync_cell_event_reset(cell);
}
cell->state = SC_RESERVED;
cell->reservation_time = time(NULL);
cell->thread = os_thread_get_curr_id();
......@@ -383,6 +395,59 @@ sync_array_reserve_cell(
return;
}
/**********************************************************************
Frees the cell. Note that we don't have any mutex reserved when calling
this. */
static
void
sync_array_free_cell(
/*=================*/
sync_array_t* arr, /* in: wait array */
ulint index) /* in: index of the cell in array */
{
sync_cell_t* cell;
cell = sync_array_get_nth_cell(arr, index);
ut_a(cell->state == SC_WAKING_UP);
ut_a(cell->wait_object != NULL);
cell->state = SC_FREE;
cell->wait_object = NULL;
}
/**********************************************************************
Frees the cell safely by reserving the sync array mutex and decrementing
n_reserved if necessary. Should only be called from mutex_spin_wait. */
void
sync_array_free_cell_protected(
/*===========================*/
sync_array_t* arr, /* in: wait array */
ulint index) /* in: index of the cell in array */
{
sync_cell_t* cell;
sync_array_enter(arr);
cell = sync_array_get_nth_cell(arr, index);
ut_a(cell->state != SC_FREE);
ut_a(cell->wait_object != NULL);
/* We only need to decrement n_reserved if it has not already been
done by sync_array_signal_object. */
if (cell->state == SC_RESERVED) {
ut_a(arr->n_reserved > 0);
arr->n_reserved--;
}
cell->state = SC_FREE;
cell->wait_object = NULL;
sync_array_exit(arr);
}
/**********************************************************************
This function should be called when a thread starts to wait on
a wait array cell. In the debug version this function checks
......@@ -404,6 +469,7 @@ sync_array_wait_event(
cell = sync_array_get_nth_cell(arr, index);
ut_a((cell->state == SC_RESERVED) || (cell->state == SC_WAKING_UP));
ut_a(cell->wait_object);
ut_a(!cell->waiting);
ut_ad(os_thread_get_curr_id() == cell->thread);
......@@ -436,7 +502,8 @@ sync_array_wait_event(
}
/**********************************************************************
Reports info of a wait array cell. */
Reports info of a wait array cell. Note: sync_array_print_long_waits()
calls this without mutex protection. */
static
void
sync_array_cell_print(
......@@ -456,6 +523,9 @@ sync_array_cell_print(
(ulong) cell->line,
difftime(time(NULL), cell->reservation_time));
/* If the memory area pointed to by old_wait_mutex /
old_wait_rw_lock has been freed, this can crash. */
if (type == SYNC_MUTEX) {
/* We use old_wait_mutex in case the cell has already
been freed meanwhile */
......@@ -535,7 +605,7 @@ sync_array_find_thread(
cell = sync_array_get_nth_cell(arr, i);
if (cell->wait_object != NULL
if ((cell->state == SC_RESERVED)
&& os_thread_eq(cell->thread, thread)) {
return(cell); /* Found */
......@@ -617,6 +687,7 @@ sync_array_detect_deadlock(
rw_lock_debug_t*debug;
ut_a(arr && start && cell);
ut_ad(cell->state == SC_RESERVED);
ut_ad(cell->wait_object);
ut_ad(os_thread_get_curr_id() == start->thread);
ut_ad(depth < 100);
......@@ -784,32 +855,6 @@ sync_arr_cell_can_wake_up(
return(FALSE);
}
/**********************************************************************
Frees the cell. NOTE! sync_array_wait_event frees the cell
automatically! */
void
sync_array_free_cell(
/*=================*/
sync_array_t* arr, /* in: wait array */
ulint index) /* in: index of the cell in array */
{
sync_cell_t* cell;
sync_array_enter(arr);
cell = sync_array_get_nth_cell(arr, index);
ut_a(cell->wait_object != NULL);
cell->wait_object = NULL;
ut_a(arr->n_reserved > 0);
arr->n_reserved--;
sync_array_exit(arr);
}
/**************************************************************************
Looks for the cells in the wait array which refer to the wait object
specified, and sets their corresponding events to the signaled state. In this
......@@ -825,6 +870,7 @@ sync_array_signal_object(
sync_cell_t* cell;
ulint count;
ulint i;
ulint res_count;
sync_array_enter(arr);
......@@ -833,16 +879,23 @@ sync_array_signal_object(
i = 0;
count = 0;
while (count < arr->n_reserved) {
/* we need to store this to a local variable because it's modified
inside the loop */
res_count = arr->n_reserved;
while (count < res_count) {
cell = sync_array_get_nth_cell(arr, i);
if (cell->wait_object != NULL) {
if (cell->state == SC_RESERVED) {
count++;
if (cell->wait_object == object) {
sync_cell_event_set(cell);
ut_a(arr->n_reserved > 0);
arr->n_reserved--;
}
}
......@@ -865,23 +918,35 @@ sync_arr_wake_threads_if_sema_free(void)
sync_cell_t* cell;
ulint count;
ulint i;
ulint res_count;
sync_array_enter(arr);
i = 0;
count = 0;
while (count < arr->n_reserved) {
/* we need to store this to a local variable because it's modified
inside the loop */
res_count = arr->n_reserved;
while (count < res_count) {
cell = sync_array_get_nth_cell(arr, i);
if (cell->wait_object != NULL) {
if (cell->state == SC_RESERVED) {
count++;
if (sync_arr_cell_can_wake_up(cell)) {
ut_print_timestamp(stderr);
fprintf(stderr,
" InnoDB: warning: sync_arr_wake_threads_if_sema_free()\n"
"InnoDB: found a thread to wake up.\n");
sync_cell_event_set(cell);
ut_a(arr->n_reserved > 0);
arr->n_reserved--;
}
}
......@@ -911,7 +976,7 @@ sync_array_print_long_waits(void)
cell = sync_array_get_nth_cell(sync_primary_wait_array, i);
if (cell->wait_object != NULL
if ((cell->state != SC_FREE)
&& difftime(time(NULL), cell->reservation_time) > 240) {
fputs("InnoDB: Warning: a long semaphore wait:\n",
stderr);
......@@ -919,7 +984,7 @@ sync_array_print_long_waits(void)
noticed = TRUE;
}
if (cell->wait_object != NULL
if ((cell->state != SC_FREE)
&& difftime(time(NULL), cell->reservation_time)
> fatal_timeout) {
fatal = TRUE;
......@@ -978,7 +1043,7 @@ sync_array_output_info(
cell = sync_array_get_nth_cell(arr, i);
if (cell->wait_object != NULL) {
if (cell->state != SC_FREE) {
count++;
sync_array_cell_print(file, cell);
}
......
sync/sync0sync.c
View file @ 9fad661f
......@@ -482,7 +482,7 @@ spin_loop:
{
/* Succeeded! Free the reserved wait cell */
sync_array_free_cell(sync_primary_wait_array, index);
sync_array_free_cell_protected(sync_primary_wait_array, index);
#ifdef UNIV_SYNC_DEBUG
mutex_set_debug_info(mutex, file_name, line);
......
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