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MDEV-36868: Inconsistency when shrinking innodb_buffer_pool_size #4062

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Merged
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May 28, 2025
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MDEV-36868: Inconsistency when shrinking innodb_buffer_pool_size #4062

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9 changes: 9 additions & 0 deletions mysql-test/suite/innodb/r/innodb_buffer_pool_resize.result
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,15 @@ SET STATEMENT foreign_key_checks=0, unique_checks=0 FOR
INSERT INTO t1 SELECT seq*4,seq*4 FROM seq_1_to_262144;
SET STATEMENT foreign_key_checks=0, unique_checks=0 FOR
INSERT INTO t2 SELECT seq*4,seq*4 FROM seq_1_to_16384;
SELECT @@GLOBAL.innodb_adaptive_hash_index;
@@GLOBAL.innodb_adaptive_hash_index
1
SET STATEMENT max_statement_time=1e-9 FOR
SET GLOBAL innodb_buffer_pool_size = 7340032;
SELECT @@GLOBAL.innodb_adaptive_hash_index;
@@GLOBAL.innodb_adaptive_hash_index
1
FOUND 1 /innodb_buffer_pool_size=7m.*resized from|innodb_buffer_pool_size change aborted/ in mysqld.1.err
set global innodb_buffer_pool_size = 7340032;
select count(val) from t1;
count(val)
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10 changes: 10 additions & 0 deletions mysql-test/suite/innodb/r/innodb_buffer_pool_resize_temporary.result
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Expand Up @@ -2,6 +2,16 @@ SET @save_limit=@@GLOBAL.innodb_limit_optimistic_insert_debug;
SET @save_size=@@GLOBAL.innodb_buffer_pool_size;
SET GLOBAL innodb_limit_optimistic_insert_debug=2;
SET GLOBAL innodb_buffer_pool_size=16777216;
call mtr.add_suppression("innodb_buffer_pool_size change aborted");
SET @old_innodb_adaptive_hash_index = @@innodb_adaptive_hash_index;
SET GLOBAL innodb_adaptive_hash_index = ON;
SET STATEMENT debug_dbug='+d,buf_shrink_fail' FOR
SET GLOBAL innodb_buffer_pool_size=8388608;
ERROR HY000: innodb_buffer_pool_size change aborted
SELECT @@GLOBAL.innodb_adaptive_hash_index,@@GLOBAL.innodb_buffer_pool_size;
@@GLOBAL.innodb_adaptive_hash_index @@GLOBAL.innodb_buffer_pool_size
1 16777216
SET GLOBAL innodb_adaptive_hash_index = @old_innodb_adaptive_hash_index;
CREATE TEMPORARY TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
INSERT INTO t1 SELECT seq FROM seq_1_to_200;
SET GLOBAL innodb_max_purge_lag_wait=0;
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12 changes: 12 additions & 0 deletions mysql-test/suite/innodb/t/innodb_buffer_pool_resize.test
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
--source include/have_innodb.inc
--source include/have_sequence.inc
--source include/not_embedded.inc # there are no messages in mysqld.1.err

--echo #
--echo # MDEV-29445: Reorganize buffer pool (and remove chunks)
Expand Down Expand Up @@ -42,6 +43,17 @@ INSERT INTO t2 SELECT seq*4,seq*4 FROM seq_1_to_16384;
SET GLOBAL innodb_read_only_compressed=@save_innodb_read_only_compressed;
--enable_query_log

SELECT @@GLOBAL.innodb_adaptive_hash_index;
--error 0,ER_WRONG_USAGE
SET STATEMENT max_statement_time=1e-9 FOR
SET GLOBAL innodb_buffer_pool_size = 7340032;
SELECT @@GLOBAL.innodb_adaptive_hash_index;

--let SEARCH_FILE= $MYSQLTEST_VARDIR/log/mysqld.1.err
--let SEARCH_PATTERN= InnoDB: Trying to shrink innodb_buffer_pool_size=7m
--let SEARCH_PATTERN= innodb_buffer_pool_size=7m.*resized from|innodb_buffer_pool_size change aborted
--source include/search_pattern_in_file.inc

# Attempt to shrink the buffer pool. This may occasionally fail.
--error 0,ER_WRONG_USAGE
set global innodb_buffer_pool_size = 7340032;
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10 changes: 10 additions & 0 deletions mysql-test/suite/innodb/t/innodb_buffer_pool_resize_temporary.test
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,16 @@ SET @save_size=@@GLOBAL.innodb_buffer_pool_size;
SET GLOBAL innodb_limit_optimistic_insert_debug=2;
SET GLOBAL innodb_buffer_pool_size=16777216;

call mtr.add_suppression("innodb_buffer_pool_size change aborted");

SET @old_innodb_adaptive_hash_index = @@innodb_adaptive_hash_index;
SET GLOBAL innodb_adaptive_hash_index = ON;
--error ER_WRONG_USAGE
SET STATEMENT debug_dbug='+d,buf_shrink_fail' FOR
SET GLOBAL innodb_buffer_pool_size=8388608;
SELECT @@GLOBAL.innodb_adaptive_hash_index,@@GLOBAL.innodb_buffer_pool_size;
SET GLOBAL innodb_adaptive_hash_index = @old_innodb_adaptive_hash_index;

CREATE TEMPORARY TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
INSERT INTO t1 SELECT seq FROM seq_1_to_200;

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22 changes: 7 additions & 15 deletions storage/innobase/buf/buf0buf.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1606,6 +1606,7 @@ ATTRIBUTE_COLD buf_pool_t::shrink_status buf_pool_t::shrink(size_t size)
noexcept
{
mysql_mutex_assert_owner(&mutex);
DBUG_EXECUTE_IF("buf_shrink_fail", return SHRINK_ABORT;);
buf_load_abort();

if (!n_blocks_to_withdraw)
Expand Down Expand Up @@ -2011,25 +2012,12 @@ ATTRIBUTE_COLD void buf_pool_t::resize(size_t size, THD *thd) noexcept
if (ahi_disabled)
btr_search_enable(true);
#endif
mysql_mutex_lock(&LOCK_global_system_variables);
bool resized= n_blocks_removed < 0;
if (n_blocks_removed > 0)
{
mysql_mutex_lock(&mutex);
resized= size_in_bytes == old_size;
if (resized)
{
size_in_bytes_requested= size;
size_in_bytes= size;
}
mysql_mutex_unlock(&mutex);
}

if (resized)
if (n_blocks_removed)
sql_print_information("InnoDB: innodb_buffer_pool_size=%zum (%zu pages)"
" resized from %zum (%zu pages)",
size >> 20, n_blocks_new, old_size >> 20,
old_blocks);
mysql_mutex_lock(&LOCK_global_system_variables);
}
else
{
Expand Down Expand Up @@ -2092,6 +2080,10 @@ ATTRIBUTE_COLD void buf_pool_t::resize(size_t size, THD *thd) noexcept
mysql_mutex_unlock(&mutex);
my_printf_error(ER_WRONG_USAGE, "innodb_buffer_pool_size change aborted",
MYF(ME_ERROR_LOG));
#ifdef BTR_CUR_HASH_ADAPT
if (ahi_disabled)
btr_search_enable(true);
#endif
Comment on lines +2083 to +2086
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Can you please add a testcase to check it ? Looks like it is doable just checking checking innodb_adaptive_hash_index global which should reflect the correct state.

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ebb0063 adds a nondeterministic test for this as well as for the message that the shrinking was aborted or completed. The buffer pool size change is not always being aborted in the test.

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Why can't we add a deterministic test for this one ? It should be as simple as checking if AHI is enabled after doing a buffer pool resize, right ?

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@mariadb-DebarunBanerjee mariadb-DebarunBanerjee May 28, 2025 •
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It is being exercised with a fairly good probability, close to 50%.
close to 50% in the optimized debug build

Marko mentions in slack that the non-deterministic case does hit the code sometimes. It would still be good to have one deterministic test covering the error exit path but I leave it to Marko.

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I checked a few logs on buildbot.mariadb.org, the nondeterministic test never failed to shrink the buffer pool. So, I will add a deterministic debug-instrumented test as well.

mysql_mutex_lock(&LOCK_global_system_variables);
}

Expand Down