Face unlock should just do the alloc early [LWN.net]

Face unlock should just do the alloc early

Posted Apr 20, 2025 0:04 UTC (Sun) by mokki (subscriber, #33200)
Parent article: Improvements for the contiguous memory allocator

Is there a reason why the android face unlock cannot initiate the CMA allocation immediately after the system locks the screen?

That way it usually has few seconds to minutes of time to retry the allocation before user even starts to touch the device.

Only if the device reboots without being unlocked is the work wasted.

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Face unlock should just do the alloc early

Posted May 13, 2025 12:52 UTC (Tue) by sammythesnake (guest, #17693) [Link]

I use the setting on Android to delay locking the screen for a short period after it is turned off (largely because I'm reading something when it turns off and I want to just turn it straight back on)

Perhaps there's a synergy available here - when the screen turns off, don't actually *lock* the screen until either the required CMA allocation has been made, or some suitably finite timeout has elapsed.

That way, no use of face-unlock is delayed by difficulties with the CMA allocation unless the problem is relatively persistent.

I'm imagining that, say, 20-30 seconds is probably enough to resolve just about any difficulty that *can* be resolved by turfing out some allocations from the CMA area...? Any difficulty lasting longer than that probably doesn't benefit much from more waiting, right? Anyone have any better intuition / numbers for what delay might correspond to that threshold?