02-16-2020
Let me predict what will happen without swap:
the machine will have spikes of high load, and during the spikes will pause its productive work.
Perhaps it will even invoke the OOM process killer.
My observation: a Linux kernel needs (little) swap to smoothly handle certain workloads.
Because it never frees memory without "pressure", and because of the "unused RAM is wasted RAM" philosophy.
So, for safety have a few GB of swap! Even if the kernel.org developers plus a million followers swear these situations do not exist.
In comparison, the Solaris kernel tries to free memory as a background task, in order to avoid a sudden memory pressure. Solaris can run without swap.
However, this was obscured by ZFS, that was developed with a "only free cache under pressure" philosophy. So in Solaris with ZFS either limit the ZFS cache or have some swap!
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nswapfs(5) File Formats Manual nswapfs(5)
NAME
nswapfs - maximum number of file systems that can be enabled for swap
VALUES
Default
Allowed values
DESCRIPTION
File system swap devices are managed in a table for easier indexing in the kernel. sets the kernel variable responsible for the upper
limit on this table, and thus the upper limit to file systems which can be used for swap.
Who is Expected to Change This Tunable?
Anyone.
Restrictions on Changing
Changes to this tunable take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
If another file system swap is added to the system which would increase the number above then returns to the caller (see the swapon(2) man-
page).
What Are the Side Effects of Raising the Value?
More file systems for swap can be added to the system, and the kernel will need a little more memory for the table. A small performance
side effect of the kernel having to scan more file systems to check for a duplicate during swapon is also true, but realistically negligi-
ble.
When Should the Value of This Tunable Be Lowered?
Only if you are sure the system will never go over a certain number of swap file systems, and you wish to lower this tunable to save a
small amount of kernel memory and kernel performance during swapon operations.
What Are the Side Effects of Lowering the Value?
No side effects other than the primary and presumably desired new limitation on the number of swap file systems.
What Other Tunable Values Should Be Changed at the Same Time?
None.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its meaning changed in future releases of
HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or recommended values. For information about the effects of installation on tun-
able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was
factory installed on your system, see at
AUTHOR
was developed by HP.
Tunable Kernel Parameters nswapfs(5)