oracle mysql
5.7
在performance_schema
通过以下表展现内存信息。这些表实际engine为performance_schema。这些表数据实际是以数组的形式存储在内存中的（thread_array，memory_class_array等），这些表主要展现线程级别的内存分配，不考虑系统级别的内存分配(如
buf_pool, dict_cache 等）。
mysql> show
tables like ‘%mem%‘;
+-----------------------------------------+
|
Tables_in_performance_schema (%mem%) |
+-----------------------------------------+
|
memory_summary_by_account_by_event_name |
|
memory_summary_by_host_by_event_name |
|
memory_summary_by_thread_by_event_name |
|
memory_summary_by_user_by_event_name |
|
memory_summary_global_by_event_name |
+-----------------------------------------+
5 rows in set (0.01
sec)
表的详细作用可以参考 http://dev.mysql.com/doc/refman/5.7/en/memory-summary-tables.html
mysql>
desc memory_summary_by_thread_by_event_name;
+------------------------------+---------------------+------+-----+---------+-------+
| Field | Type |
Null | Key | Default | Extra |
+------------------------------+---------------------+------+-----+---------+-------+
| THREAD_ID |
bigint(20) unsigned | NO | | NULL | |
|
EVENT_NAME | varchar(128) | NO | | NULL | |
|
COUNT_ALLOC | bigint(20) unsigned | NO | | NULL | |
| COUNT_FREE | bigint(20) unsigned |
NO | | NULL | |
|
SUM_NUMBER_OF_BYTES_ALLOC | bigint(20) unsigned | NO | | NULL | |
|
SUM_NUMBER_OF_BYTES_FREE | bigint(20) unsigned | NO | | NULL | |
| LOW_COUNT_USED |
bigint(20) | NO | | NULL | |
|
CURRENT_COUNT_USED | bigint(20) | NO | | NULL | |
| HIGH_COUNT_USED | bigint(20) | NO |
| NULL | |
|
LOW_NUMBER_OF_BYTES_USED | bigint(20) | NO | | NULL | |
|
CURRENT_NUMBER_OF_BYTES_USED | bigint(20) | NO | | NULL | |
| HIGH_NUMBER_OF_BYTES_USED |
bigint(20) | NO | | NULL | |
+------------------------------+---------------------+------+-----+---------+-------+
12 rows in set
(0.03 sec)
mysql>
show create table memory_summary_by_thread_by_event_name\G
***************************
1. row ***************************
Table:
memory_summary_by_thread_by_event_name
Create
Table: CREATE TABLE `memory_summary_by_thread_by_event_name` (
`THREAD_ID` bigint(20) unsigned NOT
NULL,
`EVENT_NAME` varchar(128) NOT
NULL,
`COUNT_ALLOC` bigint(20) unsigned NOT
NULL,
`COUNT_FREE` bigint(20) unsigned NOT
NULL,
`SUM_NUMBER_OF_BYTES_ALLOC` bigint(20)
unsigned NOT NULL,
`SUM_NUMBER_OF_BYTES_FREE`
bigint(20) unsigned NOT NULL,
`LOW_COUNT_USED`
bigint(20) NOT NULL,
`CURRENT_COUNT_USED`
bigint(20) NOT NULL,
`HIGH_COUNT_USED`
bigint(20) NOT NULL,
`LOW_NUMBER_OF_BYTES_USED`
bigint(20) NOT NULL,
`CURRENT_NUMBER_OF_BYTES_USED`
bigint(20) NOT NULL,
`HIGH_NUMBER_OF_BYTES_USED`
bigint(20) NOT NULL
)
ENGINE=PERFORMANCE_SCHEMA DEFAULT CHARSET=utf8
1 row in set (0.00
sec)
select *
from memory_summary_by_thread_by_event_name where thread_id=1 order by
CURRENT_NUMBER_OF_BYTES_USED desc limit 10; //查看单个连接内存明细。
保存内存统计信息的结构体
struct
PFS_memory_stat
{
bool
m_used;
size_t m_alloc_count;
size_t
m_free_count;
size_t m_alloc_size;
size_t m_free_size;
size_t
m_alloc_count_capacity;
size_t m_free_count_capacity;
size_t m_alloc_size_capacity;
size_t m_free_size_capacity;
......
}
对应关系
CURRENT_COUNT_USED
= @c m_alloc_count - @c m_free_count
LOW_COUNT_USED + @c m_free_count_capacity = CURRENT_COUNT_USED
CURRENT_COUNT_USED + @c
m_alloc_count_capacity = HIGH_COUNT_USED
CURRENT_SIZE_USED = @c m_alloc_size - @c m_free_size
LOW_SIZE_USED + @c m_free_size_capacity = CURRENT_SIZE_USED
CURRENT_SIZE_USED + @c
m_alloc_size_capacity = HIGH_SIZE_USED
信息收集：
入口都在PSI_MEMORY_CALL,
内存的分配和释放都都调用此接口。
count_alloc:统计分配情况
count_free:统计释放情况
结果展示：
以memory_summary_by_thread_by_event_name表为例。其实现在storage\perfschema\table_mems_by_thread_by_event_name.cc中，其实PERFORMANCE_SCHEMA下的表记录的读取实现都在storage\perfschema目录下
make_row
：跟据不同纬度从PFS_memory_stat中构造行
read_row_values：读取设置行数据
PFS_memory_stat_row::set_field
Percona/5.5:
在 show engine innodb
status中增加了一些信息，加粗字体部分，参见crv_printf_innodb_monitor。
每个结构内存总大小是存储结构本身大小和存储结构元素大小之和
例如 Adaptive hash index
2052135264 (605538536 + 1446596728)
605538536：Adaptive hash
结构所占大小
1446596728：hash 结构存储的记录总大小
----------------------
BUFFER POOL AND
MEMORY
----------------------
Total memory
allocated 35299262464; in additional pool allocated 0
Internal hash
tables (constant factor + variable factor)
Adaptive
hash index 2052135264 (605538536 + 1446596728)
Page
hash 8851208 (buffer pool 0 only)
Dictionary cache 766503482 (141607408 + 624896074)
File system 11451832
(82672 + 11369160)
Lock system 85249560 (84999896 + 249664)
Recovery system 0 (0 +
0)
Dictionary memory allocated 624896074
Buffer pool size 2097148
Buffer pool size,
bytes 34359672832
Free
buffers 1
Database pages 2008854
Old database pages
741468
Modified db pages 214412
Pending reads
0
Pending writes: LRU 0, flush list 0,
single page 0
Pages
made young 966629375, not young 5036013048
48.43
youngs/s, 146.06 non-youngs/s
Pages
read 826958847, created 46300728, written 1281936044
31.64 reads/s, 1.79
creates/s, 28.14 writes/s
Buffer
pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead
0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 2008854, unzip_LRU len:
0
I/O
sum[9896]:cur[364], unzip sum[0]:cur[0]
附：这里Total memory allocated
，在innodb_use_sys_malloc=on,记录的是系统所有内存的分配情况，在innodb_use_sys_malloc=off 时主要记录buf_pool的内存分配，上例显示的是on的情况。这里看到Total
memory allocated 比Buffer pool size, bytes 要大些，是因为Total memory
allocated除了包含Buffer pool size, bytes，还包含page控制信息（event,metux)的，可以参考这里的改进
Maria/10.0
maria10.0
中也加入了对连接的内存监控，其实基本和RDS实现一致。在my_malloc,my_realloc，my_free接口中通过调函数update_malloc_size更新连接和全局的memory_used值。
在分配和释放的地方都通过MY_THREAD_SPECIFIC来指定内存是否从指定的连接上分配。
通过以下语句都可访问内存使用。
show full processlist;
//mem_used当前连接所占内存
show status like
‘Memory_used‘; //当前连接所占内存
show status like
‘Memory_used‘; //
mysql占用所有的内存，但不包括存储引擎层分配的内存(buf_pool,dict_cache等）
memory 监控 mysql vs percona vs maria,码迷,mamicode.com