- buf_page_cleaner is signaled when the pages are added to the flush list.
- As part of the
MDEV-27774 changes the logic to signal buf_page_cleaner
accidentally got missed due to pass-by-value issue (expected pass-by-reference).
[mtr_t::commit flow would signal page cleaner if there are modified
blocks. The object that captured modified blocks was expected to get
passed by reference but accidentally got passed by value and so
page-cleaner thread was never signaled].
[Non-availability of the flushing of-course has effect on performance as could be observed from the attached graph].
- is caused by
-
MDEV-27774
Reduce scalability bottlenecks in mtr_t::commit()
-
-
Closed
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Thank you! The following code indeed is unreachable because the object rb was being passed by value and not by reference, and only a copy of the mutable data member rb.modified was ever changed:
diff --git a/storage/innobase/mtr/mtr0mtr.cc b/storage/innobase/mtr/mtr0mtr.ccindex f486c2fe0e7..10f1d6f2d19 100644--- a/storage/innobase/mtr/mtr0mtr.cc+++ b/storage/innobase/mtr/mtr0mtr.cc@@ -462,6 +462,7 @@ void mtr_t::commit()if (rb.modified){+ ut_error;mysql_mutex_lock(&buf_pool.flush_list_mutex);buf_pool.flush_list_requests+= rb.modified;