Re: [PATCH] x86, kdump: Set crashkernel_low automatically

[Yinghai Lu]

On Mon, Mar 11, 2013 at 11:55 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 03/11/2013 11:50 AM, Yinghai Lu wrote:
>>>
>>> What is the purpose of reserving that kind of memory below 896 MB?  If
>>> you have a 32-bit system, it will likely be useless since you are
>>> robbing the primary of most of lowmem, on a 64-bit system 896 MB is not
>>> a magic value in any way...?
>>
>> We did not touch 32 bit system.
>>
>> Do you mean that we should
>> For 64bit, we should try under 4G, and then try MAXMEM
>> instead of try under 896M, then 4G, and MAXMEM?
>>
>> Try 896M at first, we will let user to avoid updating their kexec-tools.
>>
>
> Are you saying 896M is somehow hardcoded into kexec-tools?

yes, before kexec-tools 2.0.4

>
> I actually disagree with trying low memory at all.  Push kdump as high
> into the memory range as we can go, if there is a performance penalty it
> is much better to take it in the kdump kernel.

Agreed, It's better let 64 bit all use one code path.
And we can find more bugs while load them all high.
otherwise it would be hard to fix them if the bugs only happens on systems
that have bunch of dimms.

>
> All the voodoo to try to keep people from updating kexec-tools is
> disturbing; although breaking userspace is bad, updating kexec-tools is
> probably easier than updating the kernel, and carrying the voodoo on
> indefinitely has serious consequences.

Yes.

So please check you are happy with this one. -v3 that set crashkernel_low
automatically.

Thanks

Yinghai

Attachment: fix_crashkernel_low_v3.patch
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