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Operating Systems and Porting / hibernate / resume / suspend-to-disk (STD) doesn't need hardware support?
« on: June 05, 2023, 06:01:33 am »I already started another thread here about all the suspend modes, including suspend to RAM and the special modes of the POWER9 architecture. I'm starting this new thread to focus on hibernate, in other words, suspend-to-disk (STD)
There is a section about hibernation in the official Linux kernel guide. They state:
Quote
Hibernation
This state (also referred to as Suspend-to-Disk or STD) offers the greatest energy savings and can be used even in the absence of low-level platform support for system suspend.
This means it doesn't matter if POWER9 or the motherboard (Talos II, Blackbird, Condor) have any hardware support for hibernation. The suspend and resume work is all done by the operating system.
The kernel guide goes on to state:
Quote
However, it requires some low-level code for resuming the system to be present for the underlying CPU architecture.
Is that code already available in any newer kernels?
Is that code available in any alternative operating system like FreeBSD or OpenBSD?
I did a check on one of my own systems and it doesn't appear to support it, disk is missing from the output:
$ cat /sys/power/state
freeze mem
Here is the same command on an Intel host, notice the disk support is listed there:
$ cat /sys/power/state
freeze mem disk