Few improvements related to CPU cache line size and padding:

Bug #79636: CACHE_LINE_SIZE should be 128 on AArch64
Bug #79637: Hard-coded cache line size
Bug #79638: Reconcile CACHE_LINE_SIZE with CPU_LEVEL1_DCACHE_LINESIZE
Bug #79652: Suspicious padding in srv_conc_t

- changed CPU_LEVEL1_DCACHE_LINESIZE to default to 128 bytes on POWER
  and AArch64 architectures in cases when no value could be detected
  by CMake using getconf

- changed CACHE_LINE_SIZE definition in ut0counter.h to be an alias of
  CPU_LEVEL1_DCACHE_LINESIZE

- changed a number of hard-coded 64-byte cache line size values in the
  InnoDB code

- fixed insufficient padding for srv_conc members in srv0conc.cc

Ported to Mariadb by Daniel Black <daniel.black@au.ibm.com>
Added s390 cache size of 256 at same time.

cmake/cpu_info.cmake

@@ -24,7 +24,3 @@ IF(GETCONF)
     OUTPUT_VARIABLE CPU_LEVEL1_DCACHE_LINESIZE
     )
 ENDIF()
-IF(CPU_LEVEL1_DCACHE_LINESIZE AND CPU_LEVEL1_DCACHE_LINESIZE GREATER 0)
-ELSE()
-  SET(CPU_LEVEL1_DCACHE_LINESIZE 64)
-ENDIF()

include/my_global.h

@@ -1232,4 +1232,22 @@ static inline double rint(double x)
 #undef __GNUG__
 #endif
 
+/*
+  Provide defaults for the CPU cache line size, if it has not been detected by
+  CMake using getconf
+*/
+#if !defined(CPU_LEVEL1_DCACHE_LINESIZE) || CPU_LEVEL1_DCACHE_LINESIZE == 0
+  #if CPU_LEVEL1_DCACHE_LINESIZE == 0
+    #undef CPU_LEVEL1_DCACHE_LINESIZE
+  #endif
+
+  #if defined(__s390__)
+    #define CPU_LEVEL1_DCACHE_LINESIZE 256
+  #elif defined(__powerpc__) || defined(__aarch64__)
+    #define CPU_LEVEL1_DCACHE_LINESIZE 128
+  #else
+    #define CPU_LEVEL1_DCACHE_LINESIZE 64
+  #endif
+#endif
+
 #endif /* my_global_h */

storage/innobase/btr/btr0sea.cc

@@ -53,7 +53,7 @@ UNIV_INTERN ulint		btr_search_this_is_zero = 0;
 /** padding to prevent other memory update
 hotspots from residing on the same memory
 cache line as btr_search_latch */
-UNIV_INTERN byte		btr_sea_pad1[64];
+UNIV_INTERN byte		btr_sea_pad1[CACHE_LINE_SIZE];
 
 /** The latch protecting the adaptive search system: this latch protects the
 (1) positions of records on those pages where a hash index has been built.
@@ -67,7 +67,7 @@ UNIV_INTERN rw_lock_t*		btr_search_latch_temp;
 
 /** padding to prevent other memory update hotspots from residing on
 the same memory cache line */
-UNIV_INTERN byte		btr_sea_pad2[64];
+UNIV_INTERN byte		btr_sea_pad2[CACHE_LINE_SIZE];
 
 /** The adaptive hash index */
 UNIV_INTERN btr_search_sys_t*	btr_search_sys;

storage/innobase/include/log0log.h

@@ -784,7 +784,7 @@ struct log_group_t{
 
 /** Redo log buffer */
 struct log_t{
-	byte		pad[64];	/*!< padding to prevent other memory
+	byte		pad[CACHE_LINE_SIZE];	/*!< padding to prevent other memory
 					update hotspots from residing on the
 					same memory cache line */
 	lsn_t		lsn;		/*!< log sequence number */

storage/innobase/include/ut0counter.h

@@ -32,11 +32,15 @@ Created 2012/04/12 by Sunny Bains
 #include "os0thread.h"
 
 /** CPU cache line size */
-#ifdef __powerpc__
-#define CACHE_LINE_SIZE		128
+#ifndef UNIV_HOTBACKUP
+# ifdef CPU_LEVEL1_DCACHE_LINESIZE
+#  define CACHE_LINE_SIZE              CPU_LEVEL1_DCACHE_LINESIZE
+# else
+#  error CPU_LEVEL1_DCACHE_LINESIZE is undefined
+# endif /* CPU_LEVEL1_DCACHE_LINESIZE */
 #else
-#define CACHE_LINE_SIZE		64
-#endif
+# define CACHE_LINE_SIZE 64
+#endif /* UNIV_HOTBACKUP */
 
 /** Default number of slots to use in ib_counter_t */
 #define IB_N_SLOTS		64

storage/innobase/srv/srv0conc.cc

@@ -109,7 +109,7 @@ UNIV_INTERN mysql_pfs_key_t	srv_conc_mutex_key;
 
 /** Variables tracking the active and waiting threads. */
 struct srv_conc_t {
-	char		pad[64  - (sizeof(ulint) + sizeof(lint))];
+	char		pad[CACHE_LINE_SIZE  - (sizeof(ulint) + sizeof(lint))];
 
 	/** Number of transactions that have declared_to_be_inside_innodb set.
 	It used to be a non-error for this value to drop below zero temporarily.

storage/xtradb/btr/btr0sea.cc

@@ -56,7 +56,7 @@ UNIV_INTERN ulint		btr_search_this_is_zero = 0;
 /** padding to prevent other memory update
 hotspots from residing on the same memory
 cache line as btr_search_latch */
-UNIV_INTERN byte		btr_sea_pad1[64];
+UNIV_INTERN byte		btr_sea_pad1[CACHE_LINE_SIZE];
 
 /** Array of latches protecting individual AHI partitions. The latches
 protect: (1) positions of records on those pages where a hash index from the
@@ -69,7 +69,7 @@ UNIV_INTERN prio_rw_lock_t*	btr_search_latch_arr;
 
 /** padding to prevent other memory update hotspots from residing on
 the same memory cache line */
-UNIV_INTERN byte		btr_sea_pad2[64];
+UNIV_INTERN byte		btr_sea_pad2[CACHE_LINE_SIZE];
 
 /** The adaptive hash index */
 UNIV_INTERN btr_search_sys_t*	btr_search_sys;

storage/xtradb/include/log0log.h

@@ -857,7 +857,7 @@ struct log_group_t{
 
 /** Redo log buffer */
 struct log_t{
-	byte		pad[64];	/*!< padding to prevent other memory
+	byte		pad[CACHE_LINE_SIZE];	/*!< padding to prevent other memory
 					update hotspots from residing on the
 					same memory cache line */
 	lsn_t		lsn;		/*!< log sequence number */

storage/xtradb/include/trx0sys.h

@@ -674,17 +674,17 @@ struct trx_sys_t{
 	trx_id_t	max_trx_id;	/*!< The smallest number not yet
 					assigned as a transaction id or
 					transaction number */
-	char		pad1[64];	/*!< Ensure max_trx_id does not share
+	char		pad1[CACHE_LINE_SIZE];	/*!< Ensure max_trx_id does not share
 					cache line with other fields. */
 	trx_id_t*	descriptors;	/*!< Array of trx descriptors */
 	ulint		descr_n_max;	/*!< The current size of the descriptors
 					array. */
-	char		pad2[64];	/*!< Ensure static descriptor fields
+	char		pad2[CACHE_LINE_SIZE];	/*!< Ensure static descriptor fields
 					do not share cache lines with
 					descr_n_used */
 	ulint		descr_n_used;	/*!< Number of used elements in the
 					descriptors array. */
-	char		pad3[64];	/*!< Ensure descriptors do not share
+	char		pad3[CACHE_LINE_SIZE];	/*!< Ensure descriptors do not share
 					cache line with other fields */
 #ifdef UNIV_DEBUG
 	trx_id_t	rw_max_trx_id;	/*!< Max trx id of read-write transactions
@@ -694,7 +694,7 @@ struct trx_sys_t{
 					memory read-write transactions, sorted
 					on trx id, biggest first. Recovered
 					transactions are always on this list. */
-	char		pad4[64];	/*!< Ensure list base nodes do not
+	char		pad4[CACHE_LINE_SIZE];	/*!< Ensure list base nodes do not
 					share cache line with other fields */
 	trx_list_t	ro_trx_list;	/*!< List of active and committed in
 					memory read-only transactions, sorted
@@ -703,7 +703,7 @@ struct trx_sys_t{
 					is not necessary. We should exploit
 					this and increase concurrency during
 					add/remove. */
-	char		pad5[64];	/*!< Ensure list base nodes do not
+	char		pad5[CACHE_LINE_SIZE];	/*!< Ensure list base nodes do not
 					share cache line with other fields */
 	trx_list_t	mysql_trx_list;	/*!< List of transactions created
 					for MySQL. All transactions on
@@ -717,14 +717,14 @@ struct trx_sys_t{
 					mysql_trx_list may additionally contain
 					transactions that have not yet been
 					started in InnoDB. */
-	char		pad6[64];	/*!< Ensure list base nodes do not
+	char		pad6[CACHE_LINE_SIZE];	/*!< Ensure list base nodes do not
 					share cache line with other fields */
 	trx_list_t	trx_serial_list;
 					/*!< trx->no ordered List of
 					transactions in either TRX_PREPARED or
 					TRX_ACTIVE which have already been
 					assigned a serialization number */
-	char		pad7[64];	/*!< Ensure list base nodes do not
+	char		pad7[CACHE_LINE_SIZE];	/*!< Ensure list base nodes do not
 					share cache line with other fields */
 	trx_rseg_t*	const rseg_array[TRX_SYS_N_RSEGS];
 					/*!< Pointer array to rollback

storage/xtradb/include/ut0counter.h

@@ -32,11 +32,15 @@ Created 2012/04/12 by Sunny Bains
 #include "os0thread.h"
 
 /** CPU cache line size */
-#ifdef __powerpc__
-#define CACHE_LINE_SIZE		128
+#ifndef UNIV_HOTBACKUP
+# ifdef CPU_LEVEL1_DCACHE_LINESIZE
+#  define CACHE_LINE_SIZE              CPU_LEVEL1_DCACHE_LINESIZE
+# else
+#  error CPU_LEVEL1_DCACHE_LINESIZE is undefined
+# endif /* CPU_LEVEL1_DCACHE_LINESIZE */
 #else
-#define CACHE_LINE_SIZE		64
-#endif
+# define CACHE_LINE_SIZE 64
+#endif /* UNIV_HOTBACKUP */
 
 /** Default number of slots to use in ib_counter_t */
 #define IB_N_SLOTS		64

storage/xtradb/srv/srv0conc.cc

@@ -110,7 +110,7 @@ UNIV_INTERN mysql_pfs_key_t	srv_conc_mutex_key;
 
 /** Variables tracking the active and waiting threads. */
 struct srv_conc_t {
-	char		pad[64  - (sizeof(ulint) + sizeof(lint))];
+	char		pad[CACHE_LINE_SIZE  - (sizeof(ulint) + sizeof(lint))];
 
 	/** Number of transactions that have declared_to_be_inside_innodb set.
 	It used to be a non-error for this value to drop below zero temporarily.

storage/xtradb/srv/srv0srv.cc

@@ -580,11 +580,6 @@ UNIV_INTERN ib_uint64_t srv_index_page_decompressed     = 0;
 
 /* Ensure status variables are on separate cache lines */
 
-#ifdef __powerpc__
-#define CACHE_LINE_SIZE 128
-#else
-#define CACHE_LINE_SIZE 64
-#endif
 #define CACHE_ALIGNED __attribute__ ((aligned (CACHE_LINE_SIZE)))
 
 UNIV_INTERN byte