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Memory problems

AbraxasAbraxas EntrantCurrent User Role Beginner
Hi,
We are running percona-xtradb-cluster 5.6, and we are experiencing some memory problems from time to time. So far a restart was the only solution I found.
I have 3G allocated to memory buffer:
innodb_buffer_pool_size = 3G
innodb_buffer_pool_instances = 2

The innodb engine status looks like this:
*************************** 1. row ***************************
Type: InnoDB
Name:
Status:
=====================================
2017-12-07 10:06:23 7fb3690e1700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 3 seconds
BACKGROUND THREAD
srv_master_thread loops: 1655915 srv_active, 0 srv_shutdown, 5637776 srv_idle
srv_master_thread log flush and writes: 7293510
SEMAPHORES
OS WAIT ARRAY INFO: reservation count 53195134
OS WAIT ARRAY INFO: signal count 56687384
Mutex spin waits 72499203, rounds 1361471924, OS waits 11228972
RW-shared spins 14622231, rounds 390995632, OS waits 10490135
RW-excl spins 14109990, rounds 840417647, OS waits 12102118
Spin rounds per wait: 18.78 mutex, 26.74 RW-shared, 59.56 RW-excl
TRANSACTIONS
Trx id counter 3839960741
Purge done for trx's n:o < 3839960741 undo n:o < 0 state: running but idle
History list length 2852
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 1941619, OS thread handle 0x7fb3690e1700, query id 1211959458 localhost root init
show engine innodb status
---TRANSACTION 3835508202, not started
MySQL thread id 1886179, OS thread handle 0x7fb273ce8700, query id 1211547418 10.2.203.68 valil cleaning up
---TRANSACTION 0, not started
MySQL thread id 1886178, OS thread handle 0x7fb369163700, query id 1211547417 10.2.203.68 valil cleaning up
---TRANSACTION 3839960735, not started
MySQL thread id 1, OS thread handle 0x7fb3691e5700, query id 1211959450 Slave has read all relay log; waiting for the slave I/O thread to update it
FILE I/O
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] ,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
110595766 OS file reads, 1333856377 OS file writes, 36003312 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
INSERT BUFFER AND ADAPTIVE HASH INDEX
Ibuf: size 1, free list len 65858, seg size 65860, 3485666 merges
merged operations:
insert 14044836, delete mark 300930432, delete 37437707
discarded operations:
insert 17371, delete mark 0, delete 0
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 7973454295079
Log flushed up to 7973454295079
Pages flushed up to 7973454295079
Last checkpoint at 7973454295079
Max checkpoint age 80826164
Checkpoint age target 78300347
Modified age 0
Checkpoint age 0
0 pending log writes, 0 pending chkp writes
602308662 log i/o's done, 0.00 log i/o's/second
BUFFER POOL AND MEMORY
Total memory allocated 3296722944; in additional pool allocated 0
Total memory allocated by read views 424
Internal hash tables (constant factor + variable factor)
Adaptive hash index 140001856 (50999768 + 89002088)
Page hash 1594568 (buffer pool 0 only)
Dictionary cache 27896518 (12751472 + 15145046)
File system 1977808 (812272 + 1165536)
Lock system 7970936 (7969496 + 1440)
Recovery system 0 (0 + 0)
Dictionary memory allocated 15145046
Buffer pool size 196606
Buffer pool size, bytes 3221192704
Free buffers 2048
Database pages 189126
Old database pages 69773
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 47645180, not young 2494521231
0.00 youngs/s, 0.00 non-youngs/s
Pages read 110588897, created 48491789, written 711001857
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 189126, unzip_LRU len: 0
I/O sum[10404]:cur[0], unzip sum[0]:cur[0]
INDIVIDUAL BUFFER POOL INFO
---BUFFER POOL 0
Buffer pool size 98303
Buffer pool size, bytes 1610596352
Free buffers 1024
Database pages 94562
Old database pages 34886
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 23758299, not young 1217773446
0.00 youngs/s, 0.00 non-youngs/s
Pages read 55098024, created 24291393, written 368564268
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 94562, unzip_LRU len: 0
I/O sum[5202]:cur[0], unzip sum[0]:cur[0]
---BUFFER POOL 1
Buffer pool size 98303
Buffer pool size, bytes 1610596352
Free buffers 1024
Database pages 94564
Old database pages 34887
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 23886881, not young 1276747785
0.00 youngs/s, 0.00 non-youngs/s
Pages read 55490873, created 24200396, written 342437589
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 94564, unzip_LRU len: 0
I/O sum[5202]:cur[0], unzip sum[0]:cur[0]
ROW OPERATIONS
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
0 RW transactions active inside InnoDB
0 RO transactions active inside InnoDB
0 out of 1000 descriptors used
Main thread process no. 3488, id 140404475774720, state: sleeping
Number of rows inserted 929252828, updated 307342247, deleted 193739747, read 18770419699
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
END OF INNODB MONITOR OUTPUT
============================

The problem is that the mysql process is using a lot more RAM than this:

# ps -aux | grep mysql
root 2876 0.0 0.0 4180 580 ? S Sep13 0:00 /bin/sh /usr/bin/mysqld_safe
mysql 3488 3.6 70.8 6478772 5786208 ? Sl Sep13 4413:09 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib/mysql/plugin --user=mysql --log-error=/var/log/mysql/error.log --pid-file=/var/run/mysqld/mysqld.pid --socket=/var/run/mysqld/mysqld.sock --port=3306 --wsrep_start_position=00000000-0000-0000-0000-000000000000:-1
root 3685 0.0 0.0 40220 4160 pts/1 S+ 10:05 0:00 mysql -uroot -px xxxxxx osbp -A

Any idea why are there extra more than 2G used?

Thank you,
Alex

Comments

  • krunalbauskarkrunalbauskar Advisor Inactive User Role Novice
    There are multiple reason:
    a. PXC maintains an incoming write-set queue.
    b. GCache is memory mapped
    c. Certification queue that also takes over memory.
  • AbraxasAbraxas Entrant Current User Role Beginner
    Thank you for the reply!
    At this point we use a master-slaves architecture (GTID), and this happened on one of the slaves. Is there a way too check the incoming write-set queue size?
    There is no GCache file or certification.

    Thank you,
    Alex
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