[MDEV-25513] raise systemd LimitNOFILE limits to match server defaults (~32768) Created: 2021-04-25  Updated: 2021-04-27  Resolved: 2021-04-26

Status: Closed
Project: MariaDB Server
Component/s: Packaging
Affects Version/s: 10.3.27, 10.5.9
Fix Version/s: 10.2.38, 10.3.29, 10.4.19, 10.5.10, 10.6.1

Type: Bug Priority: Minor
Reporter: Daniel Lewart Assignee: Daniel Black
Resolution: Fixed Votes: 0
Labels: None
Environment:

Debian 10 (buster) and Debian 11 (bullseye)


 Description   

Starting MariaDB with default configuration causes the following problems:

  • "[Warning] Could not increase number of max_open_files to more than 16384 (request: 32186)"
  • silently reduces table_open_cache_instances from 8 (default) to 4

Default Server System Variables:

  • extra_max_connections = 1
  • max_connections = 151
  • table_open_cache = 2000
  • table_open_cache_instances = 8
  • thread_pool_size = 4

LimitNOFILE=16834 is in the following files:

  • support-files/mariadb.service.in
  • support-files/mariadb@.service.in

Looking at sql/mysqld.cc lines 3837-3917:
wanted_files= (extra_files + max_connections + extra_max_connections +
tc_size * 2 * tc_instances);
wanted_files+= threadpool_size;

Plugging in the default values:
wanted_files = (30 + 151 + 1 + 2000 * 2 * 8 + 4) = 32186

However, systemd configuration has LimitNOFILE = 16384, which is far smaller.

I suggest increasing LimitNOFILE to 32768.

Thank you!
Daniel Lewart
Urbana, Illinois

 Comments   
Comment by Daniel Black [ 2021-04-26 ]

Good request Daniel.

Same applies for 10.2

4484	    // add epoll or kevent fd for each threadpool group, in case pool of threads is used
 
4485	    wanted_files+= (thread_handling > SCHEDULER_NO_THREADS) ? 0 : threadpool_size;
 
(gdb) p tc_size
 
$1 = 2000
 
(gdb) p tc_instances
 
$2 = 8
 
(gdb) p extra_files
 
$3 = 30
 
(gdb) p max_connections
 
$4 = 151
 
(gdb) p extra_max_connections
 
$5 = 1
 
(gdb) n
 
4482	                   tc_size * 2 * tc_instances);
 
(gdb) n
 
4481	    wanted_files= (extra_files + max_connections + extra_max_connections +
 
(gdb) n
 
4485	    wanted_files+= (thread_handling > SCHEDULER_NO_THREADS) ? 0 : threadpool_size;
 
(gdb) p wanted_files
 
$6 = <optimized out>
 
(gdb) n
 
4488	    min_tc_size= MY_MIN(tc_size, TABLE_OPEN_CACHE_MIN);
 
(gdb) p wanted_files
 
$7 = 32190

Comment by Daniel Black [ 2021-04-26 ]

Done. Thanks for the bug report.

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