Hi Simon,

Great answer. Indeed, it seems that is working. I tried both: jemalloc and tcmalloc. See the graph below.

- jemalloc, was implemented first, around 10:30. Memory increases almost like before. In 90 minutes, memory usage increased from ~20% to 52% (the same as the default system malloc)

- tcmalloc, implemented around 12:00. This time, much better. Memory usage started to increase very slowly and around 4pm it stabilized at 47% (approx 4Gb Ram from total 7.8)

According to my calculation and to mysqlcalculator.com, this is the expected usage (around 4Gb).

In my case, jemalloc was not efficient. I found a short explanation here:

https://www.managedserver.eu/Improve-mysql-and-mariadb-performance-with-memory-allocators-like-jemalloc-and-tcmalloc/

"If your database has memory fragmentation problems, Jemalloc is the best choice.
If you need to reduce latency in multi-threaded workloads, TCMalloc can offer superior benefits."

I used libtcmalloc.so.4 by installing google-perftools (apt-get install google-perftools)

MariaDB [mysql]> show global variables like '%malloc%';
Connection id:    327
Current database: mysql

+------------------------+--------------------------+
| Variable_name          | Value                    |
+------------------------+--------------------------+
| version_malloc_library | tcmalloc gperftools 2.10 |
+------------------------+--------------------------+
1 row in set (0.022 sec)

MariaDB [mysql]>

Now I am continuing to monitor it. I'll come back tomorrow with more data.

Regards,

Catal

On Thu, Apr 3, 2025 at 8:40 AM Simon Avery <Simon.Avery@atass-sports.co.uk> wrote:

Hi Catal

 

From experience, in most cases where a mariadb server uses more memory than expected, especially if it’s consistently growing to the point of oomkiller taking it out, the culprit has been the default malloc handler on the OS.  I’ve found this both on various flavours of EL (Centos and Rocky, 6-9) as well as Debian 12.

As it’s a bit of a FAQ, I jotted down how we solve it by using jemalloc or tcmalloc, both of which work well with MariaDb on linux.

 

https://digdilem.org/2025/03/solving-excess-memory-usage-in-mariadb/

I would suggest trying that before going further. It’s a quick and cheap fix, and if it doesn’t work, easy to revert.

Regards, Simon

See below:
Operating system: "Debian 12.10 (bookworm)"

MariaDB Version: 10.11.11-MariaDB-0+deb12u1-log

 

The server was configured (limited) to use for InnoDB -> max 3GB Ram

 

MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE 'innodb_buffer_pool_size';
+-------------------------+------------+
| Variable_name           | Value      |
+-------------------------+------------+
| innodb_buffer_pool_size | 3221225472 |
+-------------------------+------------+
1 row in set (0.001 sec)

 

But, on that server we are running also MySam, Memory and Innodb, in total, ~70 databases (8 MySam, 1 MEMORY, and the rest are InnoDB)

 

MariaDB [mysql]> select count(distinct db) from db;
+--------------------+
| count(distinct db) |
+--------------------+
|                 73 |
+--------------------+
1 row in set (0.001 sec)
MariaDB [mysql]>

 

SYSTEM 4CPU, 7.8GB RAM

 

root@adsns-db-node0:~# df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            3.8G     0  3.8G   0% /dev
tmpfs           776M  764K  775M   1% /run
/dev/sda1       150G   48G   97G  34% /
tmpfs           3.8G     0  3.8G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/sda15      241M  138K  241M   1% /boot/efi
tmpfs           776M     0  776M   0% /run/user/0
root@adsns-db-node0:~#

I found some articles on internet regarding /dev/shm, which could influence mysql performance.

In my case /dev/shm is not used even defined, so the system could use the whole available RAM - 7.8GB RAM, so I excluded this as possible cause.

 

MariaDB [(none)]> SHOW VARIABLES LIKE '%buffer_size%';
+----------------------------+-----------+
| Variable_name              | Value     |
+----------------------------+-----------+
| aria_pagecache_buffer_size | 134217728 |
| aria_sort_buffer_size      | 268434432 |
| bulk_insert_buffer_size    | 8388608   |
| innodb_log_buffer_size     | 16777216  |
| innodb_sort_buffer_size    | 1048576   |
| join_buffer_size           | 4194304   |
| key_buffer_size            | 10485760  |
| mrr_buffer_size            | 262144    |
| myisam_sort_buffer_size    | 134216704 |
| preload_buffer_size        | 32768     |
| read_buffer_size           | 131072    |
| read_rnd_buffer_size       | 262144    |
| sort_buffer_size           | 2097152   |
+----------------------------+-----------+
13 rows in set (0.001 sec)

 

Traffic is not high, just 123 queries per second.

 

MariaDB [(none)]> status;
--------------
mysql  Ver 15.1 Distrib 10.11.11-MariaDB, for debian-linux-gnu (x86_64) using  EditLine wrapper

Connection id: 877596
Current database:
Current user: root@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server: MariaDB
Server version: 10.11.11-MariaDB-0+deb12u1-log Debian 12
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: utf8mb4
Db     characterset: utf8mb4
Client characterset: utf8mb3
Conn.  characterset: utf8mb3
UNIX socket: /run/mysqld/mysqld.sock
Uptime: 7 days 3 hours 24 min 6 sec

Threads: 78  Questions: 75901186  Slow queries: 4891595  Opens: 12573592  Open tables: 2000  Queries per second avg: 123.007
--------------

MariaDB [(none)]>

 

Even I am restarting mariadb, after a short time, the memory usage is 85%

 

root@adsns-db-node0:~# free -g
               total        used        free      shared  buff/cache   available
Mem:               7           6           0           0           0           1
Swap:              0           0           0
root@adsns-db-node0:~#

 

The swap is not used, just the memory, which is ok.

CPU usage is less than ~10%, so is ok.

 

See below, output of top.

%Cpu(s):  2.2 us,  0.7 sy,  0.0 ni, 96.2 id,  0.4 wa,  0.0 hi,  0.4 si,  0.0 st
MiB Mem :   7750.8 total,    161.4 free,   6351.8 used,    712.6 buff/cache    
MiB Swap:      0.0 total,      0.0 free,      0.0 used.   1399.0 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND  
1555028 mysql     20   0 7752424   6.5g  15476 S  10.6  85.2 188:29.16 mariadbd

 

root@adsns-db-node0:~# pstree |grep maria
        |-mariadbd---51*[{mariadbd}]
root@adsns-db-node0:~#

 

All 51 childs of mariadb are using 85% from the system memory (each child ~1.6% of total RAM).

 

I found a mysql calculator and changing innodb_buffer_pool_size - its default value 8M - with 3G, I got ~3.7GB ... still not 6.6G (aprox 85% from total RAM).

See: https://www.mysqlcalculator.com/

 

5. Why this difference, from 3.7GB up to 6.6GB?

6. Where could it be the rest of 2GB which is used by mariadb (from 3.7GB up to 6.6GB)?

 

Any help will be appreciated.

Catal

 

 

From: cata via discuss <discuss@lists.mariadb.org>
Sent: 02 April 2025 15:27
To: discuss@lists.mariadb.org
Subject: [MariaDB discuss] it is normal to have a memory usage of 85%?

 

Hi everybody,

 

I am new here and I am confronted with a situation, so I will start with the questions first:

 

1. It is normal that on my server, mariadb to use almost 85% of available ram or something is wrong?

2. In case I want to limit the whole application (mariadb) to not use more than 5.5 GB RAM from total of 7.8GB it could be possible - without affecting it's performance?

3. Is anything to optimize (change) now? If yes, which variable?

4. Do we need more RAM for this server or actual RAM could be enough?