memfd_secret() in 5.14 [LWN.net]

memfd_secret() in 5.14

Posted Aug 8, 2021 0:45 UTC (Sun) by mjg59 (subscriber, #23239)
In reply to: memfd_secret() in 5.14 by Wol
Parent article: memfd_secret() in 5.14

> Because a hibernated laptop is SWITCHED OFF!

Modern hardware has basically the same set of wakeup events when powered down as it does when suspended. The embedded controller is powered and can turn the machine back on whenever it feels like it. Unless you actually pull the battery, "Switched off" doesn't mean what you think it means - the only meaningful distinction between suspend and off is whether or not the RAM is in self-refresh.

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memfd_secret() in 5.14

Posted Aug 8, 2021 9:57 UTC (Sun) by Wol (subscriber, #4433) [Link] (1 responses)

Yup. And as I understand it, that's the difference between sleep and hibernate. Hibernate also means ram-refresh is OFF.

Which, when you're off-grid and battery life is critical, is important.

And I don't know which, in general, uses more battery. Rebooting? or restoring from hibernate? My gut feel is hibernate is likely to use less battery, because it doesn''t go through the (possibly) long start up sequence before getting to a usable system.

Cheers,
Wol

memfd_secret() in 5.14

Posted Aug 8, 2021 17:25 UTC (Sun) by mjg59 (subscriber, #23239) [Link]

That's relevant in terms of how long a device can keep state, but not relevant to whether it'll catch fire in your bag.