A bit of history

A bit of history

Thanks dlang - nice summary of that LKML thread.

One thing I noticed in the thread is that if one wants to write the full image of memory, all processes must get frozen to prevent memory modification, according to designer of Suspend2, Nigel. This is something Linus didn't take into account, I think.

Also, these days many people set their systems up to suspend to disk, but then enter suspend to RAM after the image has been written to disk. This approach guarantees minimum resume time as long as the system has uninterrupted power and also guarantees resume if the power is lost. With current design, I think ACPI is instructed to set the suspend state after writing the image, given that everything is already suspened. With the new design, suspend round would have to follow snapshot, leaving the system in a slightly different state than when the snapshot was taken.

In any event, I have no idea why users have to suffer inferior solutions while the new stuff is being developed. I'm guessing because Linus thinks that suspending to disk as a concept is wrong or something and is personally not interested in it. In the meantime, users find it indispensable.

Suspend2 should have been merged long, long time ago - it's just that the subsystem maintainer is bent on not having it. Everybody had to endure his "too many lines of kernel code" arguments, which we now know are nonsense. Kernel is always supposed to get more sophisticated - this is how it's been for a long time now - and it's not about to change.

Sure, like any piece of software, Suspend2 has problems, but Nigel has always been extremely responsive. And, at the end if the day, neither swsusp nor uswsusp can do many things that Suspend2 can. So, while we're waiting for the next technology to be written, we should have the best.

Note: you can avoid this step in the future by logging into your LWN account.