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MDEV-24109 InnoDB hangs with innodb_flush_sync=OFF

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MDEV-23855 broke the handling of innodb_flush_sync=OFF.
That parameter is supposed to limit the page write rate
in case the log capacity is being exceeded and log checkpoints
are needed.

With this fix, the following should pass:
./mtr --mysqld=--loose-innodb-flush-sync=0

One of our best regression tests for page flushing is
encryption.innochecksum. With innodb_page_size=16k and
innodb_flush_sync=OFF it would likely hang without this fix.

log_sys.last_checkpoint_lsn: Declare as Atomic_relaxed<lsn_t>
so that we are allowed to read the value while not holding
log_sys.mutex.

buf_flush_wait_flushed(): Let the page cleaner perform the flushing
also if innodb_flush_sync=OFF. After the page cleaner has
completed, perform a checkpoint if it is needed, because
buf_flush_sync_for_checkpoint() will not be run if
innodb_flush_sync=OFF.

buf_flush_ahead(): Simplify the condition. We do not really care
whether buf_flush_page_cleaner() is running.

buf_flush_page_cleaner(): Evaluate innodb_flush_sync at the low
level. If innodb_flush_sync=OFF, rate-limit the batches to
innodb_io_capacity_max pages per second.

Reviewed by: Vladislav Vaintroub
This commit is contained in:
Marko Mäkelä
2020-11-04 16:55:36 +02:00
parent 7b20aa576b
commit 4cbfdeca84
7 changed files with 80 additions and 66 deletions
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7
mysql-test/suite/sys_vars/t/innodb_flush_sync_basic.test
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@@ -1,16 +1,15 @@
--source include/have_innodb.inc
SET @start_global_value = @@global.innodb_flush_sync;
SELECT @start_global_value;
#
# exists as global only
#
--echo Valid values are 'ON' and 'OFF'
select @@global.innodb_flush_sync in (0, 1);
select @@global.innodb_flush_sync;
--error ER_INCORRECT_GLOBAL_LOCAL_VAR
select @@session.innodb_flush_sync;
SET GLOBAL innodb_flush_sync = ON;
show global variables like 'innodb_flush_sync';
show session variables like 'innodb_flush_sync';
--disable_warnings
@@ -18,9 +17,6 @@ select * from information_schema.global_variables where variable_name='innodb_fl
select * from information_schema.session_variables where variable_name='innodb_flush_sync';
--enable_warnings
#
# show that it's writable
#
set global innodb_flush_sync='OFF';
select @@global.innodb_flush_sync;
--disable_warnings
@@ -74,4 +70,3 @@ set global innodb_flush_sync='AUTO';
#
SET @@global.innodb_flush_sync = @start_global_value;
SELECT @@global.innodb_flush_sync;