My Fights with Standby, Suspend to RAM and Hibernate on Linux

As the electricity prices in the UK continue to climb higher and higher I finally surrendered to the fact that using power efficient systems like diskless and thin clients is not by itself sufficient to provide me with the power bill reduction I would like to have. So I got on the S2RAM?/Hibernate train. Better late than never.

Caveats and Disappointments

Most of my PCs run diskless in order to decrease noise, maintenance costs, heat and power consumption. This all is managed via autofs propagated via NIS. Yes, I know it is like using the Death Star main armament to swat mosquitoes, but once sysadmin, you stay sysadmin.

So the first major disappointment with hibernation was that it works extremely bad on diskless or predominantly NFS systems. It takes around 90s for NFS to recover after a prolonged hibernation which makes the use of hibernate pointless. Even on machines with local disks I still keep $HOME and other key areas on a central server with a RAID array. Waiting for these to recover is a major PITA. After trying a number of equally unsuccessful tuneups I gave up and set machines to hibernate only if they have no users logged in and boot OS locally leaving only $HOME and common dirs served by NFS.

This is done using a very simple and dumb script run every 5 minutes which checks if there have been no users logged in for the last 5+ minutes. If that is the case the system tries to unmount autofs mounts and if successful goes into s2ram. The time it takes to reach a usable desktop state after wake-up is still way under 30 seconds (usually around 15) even on relatively slow systems (P3 at 1.4GHz or 1.2GHz Athlon). In fact it is less than on the same system if left always on because the file systejm cache is "frozen" while it is suspended.

User directories are still centrally managed. All machines are still fully interchangeable and any user can login on any machine. So if the significant other's PC is having a "bad hair day" she can still work on junior's PC or my office one without this being a complete disaster.

Standby

Standby on most PCs is utterly useless. With the new tickless kernels, CPU frequency throttle and ACPI support the power consumption is about the same as in idle on most systems. At the same time, some hardware like NVidia does not recover correctly after being put into standby. It is also not supported by S2RAM?.

I have tried two methods to incorporate Standby into the suspend infrastructure on Linux and I am not happy with either:

1. Modify S2RAM? source to use standby and rebuild - change the s2ramgeneric_do function in the S2RAM? source.
2. Use Hibernate.

In both cases the system continues to use about as much power as it uses it idle with current kernels. Most importantly - nvidia drivers do not like it and the systems do not recover from it.

S2RAM?

It is good when it works. Unfortunately for most older machines this is the case only on original Intel or Via motherboards. For example HP and Fujitsu/Siemens P3 and P4 using Intel OEM motherboards work. Via EPIA systems usually work as well. HP NC4000 which uses a motherboard by ALI does not. Asus P3 does not work either. Same for a few other MBs I have tried.

Newer machines mostly work out of the box .

My record with it so far has been:

S2Disk?

It works on nearly everything. However, it is rather slow as it has to go through most of the cold boot procedure.

The only modern system I have seen where it fails so far is Elite ECS GS7610 Super which is probably the worst motherboard I have seen for the last 10 years. Actually, not probably - it is the worst one.