Fedora reawakens the hibernation debate [LWN.net]

Fedora reawakens the hibernation debate

Posted Sep 18, 2018 10:49 UTC (Tue) by ibukanov (subscriber, #3942)
Parent article: Fedora reawakens the hibernation debate

Even if hibernate works, I still want to have an option to control it. As was already pointed out in the comments above, hibernation requires to enter the disk encryption password and one may or may not want to do that depending on the situation. I prefer not to enter the strong password in a cafe or other places that may have high-resolution surveillance cameras, but it is OK to do it at home or in the office.

The only automatic behavior that is probably OK is to hibernate on a low battery. But even then I prefer to have an option to keep the ram powered on after the hibernation image is written until the battery runs out.

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Fedora reawakens the hibernation debate

Posted Sep 19, 2018 3:10 UTC (Wed) by zblaxell (subscriber, #26385) [Link] (3 responses)

> The only automatic behavior that is probably OK is to hibernate on a low battery.

Bad idea. You don't know the operating environment in that situation. The laptop could be embedded in luggage with no possibility of cooling. If the laptop wakes up and hibernation hangs (e.g. because the CPU overheats itself compressing and encrypting hibernation data), the resulting confined heat will damage the hardware until the battery gives up. Usually nothing as spectacular as a fire happens, but each incident typically wipes a few percent off the battery capacity. I once had a Macbook wipe out 80% of its battery capacity in one day doing that (Linux has no monopoly on hibernate bugs).

Back in the days of spinning rust in laptops you could break the hard drives with surprise hibernations too. Even today a hot SSD is not a happy SSD, and severe data loss can be expected.

Current laptops can sit for days in suspend state. Heck, some of them now run 24+ hours while displaying a login prompt. I hardly use suspend for anything less than international travel, and I only use hibernation for dual-booting tool when a VM won't do the job.

Fedora reawakens the hibernation debate

Posted Sep 19, 2018 4:20 UTC (Wed) by Cyberax (✭ supporter ✭, #52523) [Link] (2 responses)

If your battery is down to 5% then your laptop probably won't have enough energy to overheat.

Fedora reawakens the hibernation debate

Posted Sep 19, 2018 4:35 UTC (Wed) by zblaxell (subscriber, #26385) [Link]

It's enough energy to run at full power for six minutes. With no cooling it'll easily push the air temperature in the case up to the 60C+ battery-life-shortening zone.

Fedora reawakens the hibernation debate

Posted Sep 19, 2018 12:37 UTC (Wed) by farnz (subscriber, #17727) [Link]

5% of a 50 Wh battery is still 10 kJ of energy that has to go somewhere. That's enough to push a laptop's temperature up by at least 10°C, if not more (depending on what the laptop is made of).

And note that a 50 Wh battery is not large, nor is it likely that a bag squeezed against someone's back is a cool place to begin with.