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MDEV-14529 - InnoDB rw-locks: optimize memory barriers

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Remove volatile modifier from waiters: it's not supposed for inter-thread
communication, use appropriate atomic operations instead.

Changed waiters to int32_t, my_atomic friendly type.
This commit is contained in:
Sergey Vojtovich 2017-12-01 13:37:07 +04:00
parent 57d20f1132
commit 5b624f00fc
5 changed files with 13 additions and 10 deletions
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2
storage/innobase/include/sync0rw.h
View File

@ -574,7 +574,7 @@ struct rw_lock_t
int32_t lock_word;
/** 1: there are waiters */
volatile uint32_t waiters;
int32_t waiters;
/** number of granted SX locks. */
volatile ulint sx_recursive;

5
storage/innobase/include/sync0rw.ic
View File

@ -418,7 +418,7 @@ rw_lock_x_unlock_func(
We need to signal read/write waiters.
We do not need to signal wait_ex waiters, since they cannot
exist when there is a writer. */
if (my_atomic_load32_explicit((int32*) &lock->waiters,
if (my_atomic_load32_explicit(&lock->waiters,
MY_MEMORY_ORDER_RELAXED)) {
my_atomic_store32((int32*) &lock->waiters, 0);
os_event_set(lock->event);
@ -472,7 +472,8 @@ rw_lock_sx_unlock_func(
waiters. We do not need to signal wait_ex waiters,
since they cannot exist when there is an sx-lock
holder. */
if (lock->waiters) {
if (my_atomic_load32_explicit(&lock->waiters,
MY_MEMORY_ORDER_RELAXED)) {
my_atomic_store32((int32*) &lock->waiters, 0);
os_event_set(lock->event);
sync_array_object_signalled();

3
storage/innobase/row/row0merge.cc
View File

@ -1984,7 +1984,8 @@ row_merge_read_clustered_index(
}
if (dbug_run_purge
|| dict_index_get_lock(clust_index)->waiters) {
|| my_atomic_load32_explicit(&clust_index->lock.waiters,
MY_MEMORY_ORDER_RELAXED)) {
/* There are waiters on the clustered
index tree lock, likely the purge
thread. Store and restore the cursor

7
storage/innobase/sync/sync0arr.cc
View File

@ -588,7 +588,7 @@ sync_array_cell_print(
fprintf(file,
"number of readers " ULINTPF
", waiters flag %u, "
", waiters flag %d, "
"lock_word: %x\n"
"Last time read locked in file %s line %u\n"
"Last time write locked in file %s line %u"
@ -598,7 +598,7 @@ sync_array_cell_print(
#endif
"\n",
rw_lock_get_reader_count(rwlock),
rwlock->waiters,
my_atomic_load32_explicit(&rwlock->waiters, MY_MEMORY_ORDER_RELAXED),
my_atomic_load32_explicit(&rwlock->lock_word, MY_MEMORY_ORDER_RELAXED),
innobase_basename(rwlock->last_s_file_name),
rwlock->last_s_line,
@ -1397,7 +1397,8 @@ sync_arr_fill_sys_semphore_waits_table(
//OK(fields[SYS_SEMAPHORE_WAITS_HOLDER_LINE]->store(rwlock->line, true));
//fields[SYS_SEMAPHORE_WAITS_HOLDER_LINE]->set_notnull();
OK(field_store_ulint(fields[SYS_SEMAPHORE_WAITS_READERS], rw_lock_get_reader_count(rwlock)));
OK(field_store_ulint(fields[SYS_SEMAPHORE_WAITS_WAITERS_FLAG], (longlong)rwlock->waiters));
OK(field_store_ulint(fields[SYS_SEMAPHORE_WAITS_WAITERS_FLAG],
my_atomic_load32_explicit(&rwlock->waiters, MY_MEMORY_ORDER_RELAXED)));
OK(field_store_ulint(fields[SYS_SEMAPHORE_WAITS_LOCK_WORD],
my_atomic_load32_explicit(&rwlock->lock_word, MY_MEMORY_ORDER_RELAXED)));
OK(field_store_string(fields[SYS_SEMAPHORE_WAITS_LAST_READER_FILE], innobase_basename(rwlock->last_s_file_name)));

6
storage/innobase/sync/sync0rw.cc
View File

@ -897,7 +897,7 @@ rw_lock_validate(
MY_MEMORY_ORDER_RELAXED);
ut_ad(lock->magic_n == RW_LOCK_MAGIC_N);
ut_ad(my_atomic_load32_explicit((int32*) &lock->waiters,
ut_ad(my_atomic_load32_explicit(const_cast<int32_t*>(&lock->waiters),
MY_MEMORY_ORDER_RELAXED) < 2);
ut_ad(lock_word > -(2 * X_LOCK_DECR));
ut_ad(lock_word <= X_LOCK_DECR);
@ -1166,8 +1166,8 @@ rw_lock_list_print_info(
fprintf(file, "RW-LOCK: %p ", (void*) lock);
if (lock->waiters) {
fputs(" Waiters for the lock exist\n", file);
if (int32_t waiters= my_atomic_load32_explicit(const_cast<int32_t*>(&lock->waiters), MY_MEMORY_ORDER_RELAXED)) {
fprintf(file, " (%d waiters)\n", waiters);
} else {
putc('\n', file);
}