Marko Mäkelä added a comment - 2021-02-18 14:01 Thank you for the report. This regression was caused by MDEV-24278 , which aims avoid unnecessary regular wake-up of the page cleaner thread. The following change should fix this: diff --git a/storage/innobase/buf/buf0flu.cc b/storage/innobase/buf/buf0flu.cc index 21a01dbd2fe..0acf9334c2c 100644 --- a/storage/innobase/buf/buf0flu.cc +++ b/storage/innobase/buf/buf0flu.cc @@ -2136,11 +2136,13 @@ static os_thread_ret_t DECLARE_THREAD(buf_flush_page_cleaner)(void*) double(UT_LIST_GET_LEN(buf_pool.LRU) + UT_LIST_GET_LEN(buf_pool.free)); if (lsn_limit); + else if (srv_max_dirty_pages_pct_lwm != 0.0) + { + if (dirty_pct < srv_max_dirty_pages_pct_lwm) + goto unemployed; + } else if (dirty_pct < srv_max_buf_pool_modified_pct) goto unemployed; - else if (srv_max_dirty_pages_pct_lwm == 0.0 || - dirty_pct < srv_max_dirty_pages_pct_lwm) - goto unemployed; const lsn_t oldest_lsn= buf_pool.get_oldest_modified() ->oldest_modification(); Now, how to avoid the unwanted goto unemployed if the above fix is not present? It looks like the only way to do this could be setting the two parameters to the same value. But, because the value innodb_max_dirty_pages_pct_lwm=0 is special ( MDEV-24537 ), we should use a value close to it if the aim is to have the buffer pool flushed: SET GLOBAL innodb_max_dirty_pages_pct_lwm=0.001; SET GLOBAL innodb_max_dirty_pages_pct=0.001; As far as I can, tell this bug makes the parameter innodb_max_dirty_pages_pct_lwm basically useless and prevents the adaptive flushing from working.

Marko Mäkelä added a comment - 2021-02-18 16:08 I can verify that indeed the cause of this is MDEV-24537 , which was applied after MDEV-24278 . One more change will be necessary to ensure that SET GLOBAL innodb_max_dirty_pages_pct will wake up the sleeping page cleaner thread: diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc index d306311365d..d54987889fd 100644 --- a/storage/innobase/handler/ha_innodb.cc +++ b/storage/innobase/handler/ha_innodb.cc @@ -17206,10 +17206,10 @@ innodb_max_dirty_pages_pct_update( in_val); srv_max_dirty_pages_pct_lwm = in_val; - pthread_cond_signal(&buf_pool.do_flush_list); } srv_max_buf_pool_modified_pct = in_val; + pthread_cond_signal(&buf_pool.do_flush_list); } /****************************************************************//**

Axel Schwenke added a comment - 2021-02-18 16:40 verified to work with MariaDB10.5.9 (9d7dc1f6d04)