[conspire] successful install, at last

[Rick Moen]

I wrote:

> I'm curious whether there are any stability problems if one does
> entirely without either swap partitions or swap files, on modern Linux
> systems.  Swap activity is deeply problematic on an SSD-only system
> lacking a spinning-rust drive, so I'd be interested in whether zero-swap
> operation is tenable.  I lack data from the field, and would rather
> learn from other people's experience if possible.  (Old joke:  The way
> you identify the pioneers in computing is from the arrows sticking out
> of their backs.)

Good news:  The Red Hat people say there should be no problem.
https://www.redhat.com/en/blog/do-we-really-need-swap-modern-systems


Q: Can I run without swap? Is further tuning possible?

A: Systems without swap can make sense and are supported by Red Hat -
   just be sure the behaviour of such a system under memory pressure is
   what you want. In most environments, a bit of swap makes sense.

o  /proc/meminfo Committed_AS field shows how much memory processes have
   requested.

o  Using sysctl, we can enable/disable overcommit, and configure how much
   overcommit should be allowed. The defaults need to be changed only in
   rare cases, and after properly testing the new settings. The RHEL
   Performance Tuning Guide[1]

o  A solution document with details regarding the likeliness of
   swapping[2] - for example in changing vm.swappiness. This also
   requires good testing with your applications.

o  Without swap, the system will call the OOM when the memory is
   exhausted. You can prioritize which processes get killed first in
   configuring oom_adj_score.[3] 

o  If you write an application, want to lock pages into RAM and prevent
   them from getting swapped, mlock() can be used.

o  If you design your applications to regularly use swap, make sure to
   use faster devices, like SSD - starting with Red Hat Enterprise Linux
   7.1, ‘swapon --discard’ can be used to send TRIM to SSD devices, to
   discard the device contents on swapon.

o  The Storage Administration Guide has also a section on swap
   configuration.[4]

[1] https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-memory-captun.html

[2] https://access.redhat.com/solutions/103833  (N.B.: Accessible only
to RHN subscribers.)

[3] https://access.redhat.com/solutions/1171183  (N.B.: Accessible only
to RHN subscribers.)

[4] https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Storage_Administration_Guide/ch-swapspace.html

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