Amerigo Wang <amwang@xxxxxxxxxx> writes:Sure, I have no plan to do growing reserved memory at run-time... only freeing or shrinking it...
Yes, exactly, in fact I am doing another part which will allow us to take back
of the reserved memory at run-time.
Alright. Let's look at that.
I would make the restriction you can't resize the area while a kexec
on panic image is loaded, and growing the area would not be a
realistic option.
If crash_kernel=auto happens in the context of being able to shrink
the area from user space the definition is simple. We reserve as much
memory as we think we can without affecting performance, stability,
reliability.
We can use an initial approximation of perhaps 1/32nd of low memory
(aka directly mapped memory), and I don't see a point in making the
code arch dependent at all. We should run the size approximation past
the folks on linux-mm as they are more likely to know how much memory
reduction we can tolerate without problems.
We can then plan on user space saying hey that is more than I need:
shrink that, and load the kexec on panic kernel.