Difference between revisions of "Swap/de"

Dieser Artikel versucht, so umfassend wie möglich zu sein, aber noch mehr Informationen finden Sie in den  [[Special:MyLanguage/#See_Also|unten verlinkten Artikel]]

Der "abnehmende Nutzen" bedeutet, dass Sie, wenn Sie mehr Auslagerungsspeicher als das Doppelte Ihrer RAM-Größe benötigen, besser mehr RAM hinzufügen sollten, da der Zugriff auf die Festplatte (HDD) etwa 10³ langsamer ist als der Zugriff auf den RAM, so dass etwas, das 1 Sekunde dauern würde, plötzlich mehr als 15 Minuten dauert! Und auf einem Halbleiterlaufwerk (Solid State Drive, SSD) dauert derselbe Vorgang, der im RAM 1 Sekunde dauerte, auf dem SSD immer noch etwa 1 Minute!

   if [[ $? -eq 0 ]]; then

Um eine Auslagerungspartition zu erstellen, benötigen Sie genügend nicht zugewiesenen Speicherplatz, um eine zusätzliche Partition zu erstellen. Wenn Sie nicht genügend Platz haben, springen Sie zum nächsten Abschnitt [[Special:MyLanguage/#Using_a_swap_file|#Verwenden_einer_Auslagerungsdatei]]. Eine Auslagerungspartition kann in jeder Datenträgerverwaltung / Partitionsverwaltung erstellt werden und sollte als Typ {{ic|linuxswap}} eingerichtet werden.Special:MyLanguage/#Using_a_swap_file

If you would like to have more than one swap partition, simply repeat the steps above for any additional partitions.

{{tip|There is no reason you can't have both a swap partition and a swapfile.  This is an easy way to add more swap without repartitioning.}}

Prior to running the {{ic|fallocate}} step above, you should run these commands:

These commands create an empty swapfile, disable COW for that file and ensure that compression is disabled.

{{tip|To stay compatible with Timeshift, it is necessary to create the swapfile outside the root subvolume "@".

Just replace /swapfile with /@swapfile/swapfile.}}

{{note|Using systemd-swap with on btrfs/zfs or with hibernation support requires special handling beyond the scope of this article}}

It is possible to automatically manage the size of your swapfile using {{ic|systemd-swap}}.  It can create swap files dynamically based on memory needs.  It is also an easy way to enable/manage [[#Using_zswap_with_systemd-swap|zswap]]

Next enable dynamic swap management by creating a file {{ic|/etc/systemd/swap.conf.d/myswap.conf}} with the following parameters:

If you would prefer a single command to create this file you could use:

To display your current swap devices you can use the command {{ic|swapon}}.  For example, my test machine displays the following:

In this example there are two swap devices.  A swapfile and a swap partition.  To turn them off we can use the command {{ic|swapoff}}.

We need to also remove any lines related to swap from {{ic|/etc/fstab}}.  Edit the file with an [[Special:MyLanguage/Viewing_and_editing_configuration_files|appropriate text editor]] and remove or comment out the lines for the swap space.  In the example above, we would remove these lines:

If removing hibernation entirely then also delete {{ic|resume}} from the {{ic|HOOKS}} line in {{ic|/etc/mkinitpcio.conf}} and run:

  sudo mkinitpcio -P

Next reboot.  After the reboot, when running {{ic|swapon}} you should see something similiar to the following:

systemd-swap will add and remove swapfiles as your memory usage dictates.

{{note|If you don't delete your existing swap partition it will be automatically activated by systemd even though you have removed it from fstab}}

There are couple of parameters that can be used to tune swap utilization.  These are swappiness and vfs_cache_pressure.  To see your current settings for these you can use the following commands:

{{ic|swappiness}} controls how likely a page is to be transferred to swap.  This value represents the percentage of the free memory before activating swap. The lower the value, the less swapping is used and the more memory pages are kept in physical memory where:

* 0 disables swap

* 60 is the default value which is ideal for a server that is memory-starved and running a lot of services

* 100 is very aggressive swapping.

For ''most'' desktop computers the recommended value is 10: Theoretically, this means to only start swapping when RAM usage reaches around 90 percent.

{{ic|vfs_cache_pressure}} used to be a percentage value that controls the tendency of the kernel to ''reclaim'' the memory which is used for caching of directory and inode objects with a default value of 100 on Kernels <5.4. On Kernels >=5.4 can be increased beyond 100.  Increasing this value will increase the rate in which these objects are removed from the RAM cache.  Decreasing it will allow these objects to be cached in memory longer, consuming additional RAM over time.  Depending on your specific workload, increasing or decreasing this value too far can have significant negative impacts on system performance.  Experimentation is needed to find the appropriate balance and the default value is reasonable.  In general, it is more common to optimize swappiness before experimenting with vfs_cache_pressure.

To set these values you can use the command {{ic|sysctl}}.  For example, to set the swappiness value to 10 you could use:

'''There is no preset defined answer on the optimal values for these parameters.'''  Experimentation is needed to find the optimum configuration for your specific hardware and workload.

* The Arch Wiki page on [https://wiki.archlinux.org/index.php/Swap swap]

* The Arch Wiki page on [https://wiki.archlinux.org/index.php/Zswap zswap]

* The Linux kernel documentation on [https://www.kernel.org/doc/Documentation/vm/zswap.txt zswap]

* The Linux kernel documentation on [https://www.kernel.org/doc/Documentation/sysctl/vm.txt swappiness and vfs_cache_pressure]

* The openSUSE guide to [https://doc.opensuse.org/documentation/leap/tuning/html/book.sle.tuning/cha.tuning.memory.html tuning memory]

* The [https://github.com/Nefelim4ag/systemd-swap systemd-swap page]

* The ZFS on Linux guide on [https://github.com/zfsonlinux/pkg-zfs/wiki/HOWTO-use-a-zvol-as-a-swap-device Swap Volumes]