Linux

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Linux
1. Virtual Memory
2. IO-Scheduler

Der Kernel und einige wichtige Optionen die man nicht aus dem Gedächtnis verlieren sollte.

   1 GRUB_CMDLINE_LINUX_DEFAULT="quiet zwap.enabled=1 cgroup.enable=memory swapaccount=1 scsi_mod.use_blk_mq=1 nomodeset"

Virtual Memory

https://www.kernel.org/doc/Documentation/sysctl/vm.txt
In der Voreinstellung ist die Swappiness auf 60 eingestellt.
Zwei Einstellungsmöglichkeiten
1. sysctl
2. procfs
/proc/sys/vm/swappiness

   1 root@infinitas /proc/sys/vm # cat /proc/sys/vm/swappiness
   2 60
   3 root@infinitas /proc/sys/vm # echo 5 > /proc/sys/vm/swappiness
   4 root@infinitas /proc/sys/vm # cat /proc/sys/vm/swappiness
   5 5

/etc/sysctl.d/swappiness.conf

   1 vm.swappiness = 5

Einstellungen mit sysctl anwenden.

   1 root@infinitas /proc/sys/vm # sysctl --system
   2 * Applying /etc/sysctl.d/30-baloo-inotify-limit.conf ...
   3 fs.inotify.max_user_watches = 524288
   4 * Applying /etc/sysctl.d/30-postgresql-shm.conf ...
   5 * Applying /etc/sysctl.d/30-tracker.conf ...
   6 fs.inotify.max_user_watches = 65536
   7 * Applying /usr/lib/sysctl.d/50-coredump.conf ...
   8 kernel.core_pattern = |/lib/systemd/systemd-coredump %P %u %g %s %t 9223372036854775808 %e
   9 * Applying /etc/sysctl.d/99-sysctl.conf ...
  10 * Applying /etc/sysctl.d/vm.conf ...
  11 vm.swappiness = 5
  12 vm.dirty_background_ratio = 8
  13 vm.dirty_expire_centisecs = 3000
  14 vm.dirty_ratio = 32
  15 vm.dirty_writeback_centisecs = 500
  16 * Applying /etc/sysctl.conf ...

IO-Scheduler

BLK-MQ nowadays is broadly available and enabled in distributions. Using multiple queues on multicore systems with fast storage promises some performance gains.

Activate alternative schedulers

But when i took a look on available schedulers only "mq-deadline" and "none" were available.

   1 cat /sys/class/block/sda/queue/scheduler
   2 [mq-deadline] none

They are shipped as a kernel module and need to be loaded via modprobe

   1 ls /lib/modules/$(uname -r)/kernel/block
   2 bfq.ko  kyber-iosched.ko

   1 modprobe bfq
   2 modprobe kyber-iosched

So we can make them available via /etc/modules.

Set IO-Scheduler permanently

Either with kernel-cmdline elevator=$SCHEDULER in /etc/default/grub or

via udev-rule which is some more selective:

   1 /etc/udev/rules.d/60-schedulers.rules
   2 
   3 ACTION=="add|change", KERNEL=="sda", ATTR{queue/scheduler}="bfq"
   4 ACTION=="add|change", KERNEL=="sdb", ATTR{queue/scheduler}="bfq"

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Linux

Virtual Memory

IO-Scheduler

Activate alternative schedulers

Set IO-Scheduler permanently