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SubjectRe: [PATCH v2] Do not reserve crashkernel high memory if crashkernel low memory reserving failed
On 07/21/15 at 12:22pm, Yinghai Lu wrote:
> On Tue, Jul 21, 2015 at 1:58 AM, Baoquan He <bhe@redhat.com> wrote:
>
> > Maybe system which don't need low memory is rare, only for testing?
>
> No, it is not rare.
>
> All recent intel based systems with iommu support does not need low.

Yeah, you are right.

>
> And those systems get punished by following patch:
>
> | commit 94fb9334182284e8e7e4bcb9125c25dc33af19d4
> | Author: Joerg Roedel <jroedel@suse.de>
> | Date: Wed Jun 10 17:49:42 2015 +0200
> |
> | x86/crash: Allocate enough low memory when crashkernel=high
>
> that reserve 256M low always. and those 256M get wasted.
>
> That commit should only be used to workaround some systems that
> have partial iommu support.

Those big servers mostly has hardware iommu. But they still can
enable swiotlb suport. Then low memory is needed.

>
> Yinghai


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