From Fedora Project Wiki
mNo edit summary
No edit summary
Line 1: Line 1:
"Hybrid suspend" means to do a combination of suspend-to-disk and suspend-to-ram, keeping the machine powered on until battery runs low.
'''Problem'''


Advantages of this technique are:
* users can't/shouldn't distinguish sleep and hibernation
* suspend to RAM (S3) is not robust against power loss
* we don't have anything that can reliably replace a full power off


* The user doesn't have to chose between to choices (suspend or hibernate) which are meaningless to him
'''Relevant Art'''
* No risk of loosing data when running out of battery while suspended


Disadvantages are:
Windows Vista does not use a hybrid suspend.  It seems to wake from S3 and enter S4 as necessary.
http://www.microsoft.com/windows/windows-vista/features/fast-sleep-and-resume.aspx


* It is slower than just suspend-to-ram
Apple Mac OS X seems to perform a true "hybrid suspend".  In that it means suspends state to disk before it suspends to ram.
 
'''Discussion'''
 
According to Matthew Garrett (Oct 2008):
"So what we have *now* is all the technology to do S3, resume at some later point and
then either return to S3 or if power is low, change to S4.  Why we *can't* do that under any circumstances by default is that on at least 20% of systems, resume will fail for one bullshit reason or another.  We understand all those reasons, but it's going to be at least a year until they're fixed."
 
Can we wake from S3 on a low battery condition or only after an amount of time?  Matthew says that we can "make a handwavy and conservative guess at the rate of power drain, set the alarm to wake us before 0 [power].  When we wake, recalibrate that guess and either go back to S3 or enter S4."
 
We would need to do more work to make Hibernate/S4 faster and more reliable.
 
Matthew will hopefully write up some more information about this in his blog.

Revision as of 15:16, 28 October 2008

Problem

* users can't/shouldn't distinguish sleep and hibernation 
* suspend to RAM (S3) is not robust against power loss 
* we don't have anything that can reliably replace a full power off

Relevant Art

Windows Vista does not use a hybrid suspend. It seems to wake from S3 and enter S4 as necessary.

http://www.microsoft.com/windows/windows-vista/features/fast-sleep-and-resume.aspx

Apple Mac OS X seems to perform a true "hybrid suspend". In that it means suspends state to disk before it suspends to ram.

Discussion

According to Matthew Garrett (Oct 2008): "So what we have *now* is all the technology to do S3, resume at some later point and then either return to S3 or if power is low, change to S4. Why we *can't* do that under any circumstances by default is that on at least 20% of systems, resume will fail for one bullshit reason or another. We understand all those reasons, but it's going to be at least a year until they're fixed."

Can we wake from S3 on a low battery condition or only after an amount of time? Matthew says that we can "make a handwavy and conservative guess at the rate of power drain, set the alarm to wake us before 0 [power]. When we wake, recalibrate that guess and either go back to S3 or enter S4."

We would need to do more work to make Hibernate/S4 faster and more reliable.

Matthew will hopefully write up some more information about this in his blog.