Fwd: Question about the size of VMCOREINFO

Fwd: Question about the size of VMCOREINFO

[Donny Xia]

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---------- Forwarded message ---------
From: Donny Xia <donnyxia@google.com>
Date: Wed, Aug 10, 2022 at 3:39 PM
Subject: Question about the size of VMCOREINFO
To: <dyoung@redhat.com>
Cc: <bhe@redhat.com>, <vgoyal@redhat.com>, <kexec@lists.infradead.org>


Hello Kdump Maintainers,

We utilize the kexec and kdump feature heavily to collect the crash
dump file when the kernel crashes. We write some customized values
into VMCOREINFO and we find that eventually the size of the data we
write exceeds the size of VMCOREINFO. I find that the size of
VMCOREINFO is one page, which I believe is 4k. I am wondering is there
any specific reason to choose this size? Is it possible to use a
bigger number? Any suggestions about it would be appreciated.

Thanks.

Regards,
Donny Xia

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Re: Question about the size of VMCOREINFO

[Baoquan He]

Hi,

On 08/10/22 at 03:39pm, Donny Xia wrote:
> Hello Kdump Maintainers,
> 
> We utilize the kexec and kdump feature heavily to collect the crash dump
> file when the kernel crashes. We write some customized values into
> VMCOREINFO and we find that eventually the size of the data we write
> exceeds the size of VMCOREINFO. I find that the size of VMCOREINFO is one
> page, which I believe is 4k. I am wondering is there any specific reason to
> choose this size? Is it possible to use a bigger number? Any suggestions
> about it would be appreciated.

No specific reason. Just our current usage of vmcoreinfo_data is enough to
cover our need. I don't see why you can't enlarge it to, e.g 2 pages or
more. Have you tried? E.g allocate more pages and change
VMCOREINFO_BYTES to the corresponding value.


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