Re: [PATCH 0/3] Early use of boot service memory

[Yinghai Lu]

On Mon, Nov 18, 2013 at 5:32 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 11/15/2013 10:30 AM, Vivek Goyal wrote:
>>
>> And IOMMU support is very flaky with kdump. And IOMMU's can be turned
>> off at command line. And that would force one to remove crahkernel_low=0.
>> So change of one command line option forces change of another. It is
>> complicated.
>>
>> Also there are very few systems which work with IOMMU on. A lot more
>> which work without IOMMU. We have all these DMAR issues and still nobody
>> has been able to address IOMMU issues properly.
>>
>
> Why do we need such a big bounce buffer for kdump swiotlb anyway?
> Surely the vast majority of all dump devices don't need it, so it is
> there for completeness, no?

Yes, because normal path will need that 64M+32k default.

We may reduce that amount to 16M or 18M and in second kernel let
allocate less for swiotlb.

Thanks

Yinghai
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