VSZ behaviour with MariaDB MEMORY tables

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 05 Jan 2021 17:08:57 +0000

We recently had the situation that a customer complained about the Oom killer terminating the MariaDB database instance from time to time. The MariaDB database configuration was sized quit OK (about 50% of RAM was used for the database) but they did not have swap configured.

Do not underestimate performance impacts of swapping on NUMA database systems

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 21 Jun 2019 09:26:59 +0200

If your MariaDB or MySQL database system is swapping it can have a significant impact on your database query performance! Further it can also slow down your database shutdown and thus influence the whole reboot of your machine. This is especially painful if you have only short maintenance windows or if you do not want to spend the whole night with operation tasks.

MariaDB and MySQL swap analysis

oli.sennhauser@fromdual.com (Oli Sennhauser) — Tue, 14 Aug 2018 17:51:32 +0000

# free
 total used free shared buff/cache available
Mem: 16106332 3914228 367072 296508 11825032 11441608
Swap: 31250428 182924 31067504

# cat /proc/meminfo | grep ^Swap
SwapCached: 10056 kB
SwapTotal: 31250428 kB
SwapFree: 31067504 kB

# for file in /proc/*/status ; do
 awk '/VmSwap|Name/{
 if ( $2 != "0" )
 printf $2 " " $3
 }END{ print ""}' $file
done | grep kB | sort -k 2 -n -r

mysqld 29988 kB
plasmashell 19096 kB
kwin_x11 13444 kB
Xorg 13328 kB
krunner 11200 kB
knotes 5768 kB
kded5 5016 kB
korgac 4760 kB
kglobalaccel5 3288 kB
kwalletd 3148 kB
kaccess 3148 kB
polkit-kde-auth 2704 kB
xembedsniproxy 2660 kB
akonadi_control 2652 kB
kwalletd5 2616 kB
python 2572 kB
kactivitymanage 2508 kB
klauncher 2352 kB
kdeinit5 2324 kB
ksmserver 2256 kB
python 1480 kB
pulseaudio 1312 kB
sddm-helper 1172 kB
baloo_file 1172 kB
kscreen_backend 1132 kB
mission-control 1104 kB
python 992 kB
TeamDrive.bin 772 kB
sddm 772 kB
akonadiserver 616 kB
systemd 504 kB
at-spi2-registr 488 kB
systemd 472 kB
kwrapper5 468 kB
dbus-launch 400 kB
dbus-launch 396 kB
(sd-pam) 364 kB
dbus-daemon 328 kB
(sd-pam) 300 kB
at-spi-bus-laun 264 kB
obexd 260 kB
ssh-agent 252 kB
dbus-daemon 216 kB
gnome-keyring-d 212 kB
dbus-daemon 200 kB
gpg-agent 104 kB
startkde 100 kB
skypeforlinux 64 kB
start_kdeinit 60 kB
apache2 32 kB
apache2 32 kB
apache2 32 kB
apache2 32 kB
apache2 32 kB
apache2 32 kB

# sudo smem --totals --sort=swap
 PID User Command Swap USS PSS RSS
...
 1500 root /usr/sbin/apache2 -k start 32 5616 9534 23740 
10469 www-data /usr/sbin/apache2 -k start 32 136 1421 9848 
10470 www-data /usr/sbin/apache2 -k start 32 132 1418 9848 
10471 www-data /usr/sbin/apache2 -k start 32 132 1418 9848 
10472 www-data /usr/sbin/apache2 -k start 32 132 1418 9848 
10473 www-data /usr/sbin/apache2 -k start 32 132 1418 9848 
 2111 oli /usr/lib/x86_64-linux-gnu/l 60 40 43 548 
 2291 oli /usr/share/skypeforlinux/sk 60 73920 80765 106312 
 1957 oli /bin/sh /usr/bin/startkde 100 8 54 1576 
 2050 oli /usr/bin/gpg-agent --daemon 104 256 278 1924 
 2056 oli /usr/bin/dbus-daemon --fork 200 1740 1820 4480 
 1951 oli /usr/bin/gnome-keyring-daem 212 704 887 5768 
 2132 oli /usr/bin/dbus-daemon --conf 216 712 806 3924 
 2052 oli /usr/bin/ssh-agent /usr/bin 252 204 209 908 
 2315 oli /usr/lib/bluetooth/obexd 260 1084 1345 7936 
 2127 oli /usr/lib/at-spi2-core/at-sp 264 536 625 5700 
 1228 sddm (sd-pam) 300 1412 1728 3036 
 1476 sddm /usr/bin/dbus-daemon --fork 328 56 143 2748 
 1946 oli (sd-pam) 364 1216 1615 3132 
 1475 sddm dbus-launch --autolaunch 61 396 8 28 2252 
 2055 oli /usr/bin/dbus-launch --exit 400 8 24 2160 
 1223 sddm /lib/systemd/systemd --user 444 432 995 4376 
 1937 oli /lib/systemd/systemd --user 448 404 971 4400 
 2144 oli kwrapper5 /usr/bin/ksmserve 468 4 102 6356 
 2134 oli /usr/lib/at-spi2-core/at-sp 488 268 343 5776 
 2223 oli akonadiserver 616 11196 11401 21988 
 1129 root /usr/bin/sddm 724 716 963 11848 
 2277 oli ./TeamDrive.bin autostart 772 352656 353309 365768 
 2298 oli python /usr/bin/hp-systray 992 4904 7157 15340 
 2162 oli /usr/lib/telepathy/mission- 1104 1196 1540 8640 
 2166 oli /usr/lib/x86_64-linux-gnu/l 1132 696 973 15148 
 1934 root /usr/lib/x86_64-linux-gnu/s 1172 352 802 10996 
 2177 oli /usr/bin/baloo_file 1172 74356 74784 90584 
 2208 oli /usr/bin/pulseaudio --start 1312 4520 4897 10672 
 2299 oli python /usr/bin/hp-systray 1480 3152 5448 11184 
 2146 oli /usr/bin/ksmserver 2256 5024 6013 34104 
 2115 oli kdeinit5: Running... 2324 264 748 15492 
 2116 oli klauncher [kdeinit5] --fd=9 2352 1256 1997 21712 
 2154 oli /usr/bin/kactivitymanagerd 2472 4588 5337 29772 
 2284 oli python /usr/bin/hp-systray 2572 15216 18372 37452 
 1956 oli /usr/bin/kwalletd5 --pam-lo 2616 5272 6454 37400 
 2219 oli /usr/bin/akonadi_control 2652 2048 2450 23964 
 2195 oli /usr/bin/xembedsniproxy 2660 968 1405 23600 
 2190 oli /usr/lib/x86_64-linux-gnu/l 2704 1172 1703 26716 
 1954 oli /usr/bin/kwalletd --pam-log 3144 1180 1601 12784 
 2124 oli /usr/bin/kaccess 3148 708 1110 21276 
 2151 oli /usr/bin/kglobalaccel5 3288 1316 1799 25164 
 2203 oli /usr/bin/korgac -session 10 4760 1384 2093 28576 
 2118 oli kded5 [kdeinit5] 5016 77440 78828 107932 
 2217 oli /usr/bin/knotes -session 10 5768 7048 8467 41744 
 2179 oli /usr/bin/krunner 11200 16276 19166 55272 
 1148 root /usr/lib/xorg/Xorg -noliste 13316 31464 45953 68016 
 2167 oli kwin_x11 -session 106368656 13444 35972 39318 76556 
 2186 oli /usr/bin/plasmashell --shut 19096 90608 94701 135284 
 2224 oli /usr/sbin/mysqld --defaults 29988 148588 148624 151832 
-------------------------------------------------------------------------------
 170 14 150808 4085792 4318525 6436312 

# sudo smem --totals --sort=swap | grep -e mysql -e Command
 PID User Command Swap USS PSS RSS 
 6903 mysql /home/mysql/product/mariadb 0 191000 191071 194964 
16937 mysql /home/mysql/product/mysql-8 0 358812 358865 362364 
17480 mysql /home/mysql/product/mysql-5 0 271420 273310 278692 
28484 root grep -e mysql -e Command 0 352 395 2404 
29071 mysql /bin/sh bin/mysqld_safe --d 0 152 227 1724 
29326 mysql /home/mysql/product/mysql-5 0 506848 508747 514268 
 2224 oli /usr/sbin/mysqld --defaults 29988 148588 148624 151832

Swap on FromDual GmbH

VSZ behaviour with MariaDB MEMORY tables

Do not underestimate performance impacts of swapping on NUMA database systems

MariaDB and MySQL swap analysis

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