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MDEV-25954: Trim os_aio_wait_until_no_pending_writes()

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It turns out that we had some unnecessary waits for no outstanding
write requests to exist. They were basically working around a
bug that was fixed in MDEV-25953.

On write completion callback, blocks will be marked clean.
So, it is sufficient to consult buf_pool.flush_list to determine
which writes have not been completed yet.

On FLUSH TABLES...FOR EXPORT we must still wait for all pending
asynchronous writes to complete, because buf_flush_file_space()
would merely guarantee that writes will have been initiated.
This commit is contained in:
Marko Mäkelä 2021-06-23 19:06:49 +03:00
commit 6dfd44c828
6 changed files with 15 additions and 14 deletions
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1
storage/innobase/buf/buf0dblwr.cc
View file

@ -689,7 +689,6 @@ void buf_dblwr_t::flush_buffered_writes()
{
if (!is_initialised() || !srv_use_doublewrite_buf)
{
os_aio_wait_until_no_pending_writes();
fil_flush_file_spaces();
return;
}

5
storage/innobase/buf/buf0flu.cc
View file

@ -1546,11 +1546,6 @@ static std::atomic_flag log_flush_pending;
/** Advance log_sys.get_flushed_lsn() */
static void log_flush(void *)
{
/* Between batches, we try to prevent I/O stalls by these calls.
This should not be needed for correctness. */
os_aio_wait_until_no_pending_writes();
fil_flush_file_spaces();
/* Guarantee progress for buf_flush_lists(). */
log_buffer_flush_to_disk(true);
log_flush_pending.clear();

2
storage/innobase/fil/fil0fil.cc
View file

@ -1743,8 +1743,6 @@ void fil_close_tablespace(ulint id)
Thus we can clean the tablespace out of buf_pool
completely and permanently. */
while (buf_flush_dirty_pages(id));
/* Ensure that all asynchronous IO is completed. */
os_aio_wait_until_no_pending_writes();
ut_ad(space->is_stopping());
/* If the free is successful, the X lock will be released before

7
storage/innobase/include/os0file.h
View file

@ -1111,10 +1111,9 @@ void os_aio_free();
@retval DB_IO_ERROR on I/O error */
dberr_t os_aio(const IORequest &type, void *buf, os_offset_t offset, size_t n);
/** Waits until there are no pending writes in os_aio_write_array. There can
be other, synchronous, pending writes. */
void
os_aio_wait_until_no_pending_writes();
/** Wait until there are no pending asynchronous writes.
Only used on FLUSH TABLES...FOR EXPORT. */
void os_aio_wait_until_no_pending_writes();
/** Prints info of the aio arrays.

4
storage/innobase/os/os0file.cc
View file

@ -3788,8 +3788,8 @@ static void os_aio_wait_until_no_pending_writes_low()
tpool::tpool_wait_end();
}
/** Waits until there are no pending writes. There can
be other, synchronous, pending writes. */
/** Wait until there are no pending asynchronous writes.
Only used on FLUSH TABLES...FOR EXPORT. */
void os_aio_wait_until_no_pending_writes()
{
os_aio_wait_until_no_pending_writes_low();

10
storage/innobase/row/row0import.cc
View file

@ -4234,6 +4234,16 @@ row_import_for_mysql(
of delete marked records that couldn't be purged in Phase I. */
while (buf_flush_dirty_pages(prebuilt->table->space_id));
for (ulint count = 0; prebuilt->table->space->referenced(); count++) {
/* Issue a warning every 10.24 seconds, starting after
2.56 seconds */
if ((count & 511) == 128) {
ib::warn() << "Waiting for flush to complete on "
<< prebuilt->table->name;
}
os_thread_sleep(20000);
}
ib::info() << "Phase IV - Flush complete";
prebuilt->table->space->set_imported();