commit f40d1ce04231e9777a624180646736159dcd2f6b
Author: zhangxizhe <zhangxizhe.zxz@alibaba-inc.com>
Date:   Mon Mar 18 10:43:33 2024 +0800

    Align Delegate::lock to 64
    
    Background
    ==========
    Every transaction THD will call the corresponding method (e.g. before_commit()) of
    `transaction_delegate` at different stages to execute the callback function of the
    registered Observers. This part of the code will be protected by calling
    `Delegate:read_lock()`, which uses a `pthread_rwlock_t` (64B) RW lock. However, the
    memory allocation of `transaction_delegate` is aligned to 16, and the `Delegate::lock`
    may not be loaded into only one Cache Line (64B), which makes access to the lock slower.
    This can lead to performance degradation when concurrency is high.
    
    See https://bugs.mysql.com/bug.php?id=114361 for details.
    
    Implementation
    ==============
    Declare Delegate::lock to be aligned to 64.

diff --git a/sql/rpl_handler.h b/sql/rpl_handler.h
index d06f4c8071b..d34e042d471 100644
--- a/sql/rpl_handler.h
+++ b/sql/rpl_handler.h
@@ -211,9 +211,11 @@ class Delegate {
   /** List of registered observers */
   Observer_info_list observer_info_list;
   /**
-    A read/write lock to be used when not optimizing for static plugin config
+    A read/write lock to be used when not optimizing for static plugin config.
+    Align lock to CPU_LEVEL1_DCACHE_LINESIZE to ensure it can be loaded into
+    one Cache Line, reduce performance loss in high concurrency scenarios.
    */
-  mysql_rwlock_t lock;
+  alignas(CPU_LEVEL1_DCACHE_LINESIZE) mysql_rwlock_t lock;
   /**
     A shared-exclusive spin lock to be used when optimizing for static plugin
     config.