| Bug #103391 | buf_get_LRU_mutex can be optimized for flushing from FLUSH_LIST | ||
|---|---|---|---|
| Submitted: | 21 Apr 2021 4:24 | Modified: | 14 May 2021 13:03 |
| Reporter: | zhai weixiang (OCA) | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: InnoDB storage engine | Severity: | S3 (Non-critical) |
| Version: | 8.0.24 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
[21 Apr 2021 7:19]
MySQL Verification Team
Hello Zhai, Thank you for the report and feedback. regards, Umesh
[14 May 2021 13:03]
Daniel Price
Posted by developer: Fixed as of the upcoming 8.0.26 release, and here's the proposed changelog entry from the documentation team: The buf_get_LRU_mutex() function was optimized to avoid acquiring the LRU mutex unnecessarily when flushing from the flush list.
Description: In function buf_get_LRU_mutex, if the flushing is from flush_list, it may acquire lru_mutex and then release it immediately, actually we can skip acquire/release lru mutex in such case. How to repeat: read the code Suggested fix: diff --git a/storage/innobase/buf/buf0buf.cc b/storage/innobase/buf/buf0buf.cc index c79377c..b423331 100644 --- a/storage/innobase/buf/buf0buf.cc +++ b/storage/innobase/buf/buf0buf.cc @@ -5212,24 +5212,21 @@ static bool buf_get_LRU_mutex(buf_page_t *bpage) noexcept { auto buf_pool = buf_pool_from_bpage(bpage); const auto flush_type = buf_page_get_flush_type(bpage); - mutex_enter(&buf_pool->LRU_list_mutex); - - auto block_mutex = buf_page_get_mutex(bpage); - mutex_enter(block_mutex); - - if ( + bool will_hold_mutex = ( #if defined UNIV_DEBUG || defined UNIV_BUF_DEBUG /* To keep consistency at buf_LRU_insert_zip_clean() */ buf_page_get_state(bpage) == BUF_BLOCK_ZIP_DIRTY || #endif /* UNIV_DEBUG || UNIV_BUF_DEBUG */ - flush_type == BUF_FLUSH_LRU || flush_type == BUF_FLUSH_SINGLE_PAGE) { + flush_type == BUF_FLUSH_LRU || flush_type == BUF_FLUSH_SINGLE_PAGE); - return true; + if (will_hold_mutex) { + mutex_enter(&buf_pool->LRU_list_mutex); } - mutex_exit(&buf_pool->LRU_list_mutex); + auto block_mutex = buf_page_get_mutex(bpage); + mutex_enter(block_mutex); - return false; + return will_hold_mutex; }