Messages in this thread | | | Date | Tue, 21 Jul 2015 16:19:32 +0800 | From | Dave Young <> | Subject | Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel low memory reserving failed |
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On 07/21/15 at 09:38am, Ingo Molnar wrote: > > * Dave Young <dyoung@redhat.com> wrote: > > > Hi, Baoquan > > > > The interface was introduced by Yinghai, ccing him. > > Also, why was this syntax introduced in the first place? Why should the user > care??
The history is like below, I might miss something, Yinghai/HPA/Vivek may correct and provide more background:
First commit is below: commit 7d41a8a4a2b2438621a9159477bff36a11d79a42 Author: Yinghai Lu <yinghai@kernel.org> Date: Thu Jan 24 12:20:10 2013 -0800
x86, kdump: Remove crashkernel range find limit for 64bit
Previously kdump reservation is limited to <896M, above commit remove the limitation. Then because of kdump kernel need access low mem for swiotlb buffer, thus there's commit below:
commit 0212f9159694be61c6bc52e925fa76643e0c1abf Author: Yinghai Lu <yinghai@kernel.org> Date: Thu Jan 24 12:20:11 2013 -0800
x86: Add Crash kernel low reservation
Later, Vivek found old kexec-tools does not work, then Yinghai introduced new param crashkernel_high=:
commit 55a20ee7804ab64ac90bcdd4e2868a42829e2784 Author: Yinghai Lu <yinghai@kernel.org> Date: Mon Apr 15 22:23:47 2013 -0700
x86, kdump: Retore crashkernel= to allocate under 896M
Finally it becomes crashkernel=x,high: commit adbc742bf78695bb98c79d18c558b61571748b99 Author: Yinghai Lu <yinghai@kernel.org> Date: Mon Apr 15 22:23:48 2013 -0700
x86, kdump: Change crashkernel_high/low= to crashkernel=,high/low
> > We should only have a single crashkernel option, to enable it - and everything > else should be figured out by the kernel, automatically.
Presonally I do not current complicated params either, I hope we can have an elegant interface, but seems there's no better way to resolve the low memory only requirement for software tlb.
> > Any other sub-options just paper over some fragility elsewhere and make the > feature harder to use, hence more fragile.
Agree, it is becoming worse..
Thanks Dave
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