Messages in this thread | | | Date | Thu, 06 Aug 2009 17:11:48 +0800 | From | Amerigo Wang <> | Subject | Re: [Patch 0/7] Implement crashkernel=auto |
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Eric W. Biederman wrote: > Amerigo Wang <amwang@redhat.com> writes: > >> 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. > > Sure, I have no plan to do growing reserved memory at run-time... only freeing or shrinking it...
> 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. > >
Yup, agreed.
> We can then plan on user space saying hey that is more than I need: > shrink that, and load the kexec on panic kernel. >
Exactly... but the interface still needs to be discussed...
Currently, we have two options:
1) add a new flag to kexec_load(2) to tell the kernel to shrink the memory; 2) use /proc/iomem, let the user to decide which and how much of the reserved memory should be removed.
Any thoughts?
Thanks.
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