Subject: Re: [PATCH 1/2] mm: Allow disabling deferred struct page initialisation

From: Dave Hansen <[email-masked]>
Date: Wed, 3 Aug 2016 11:17:43 -0700

On 08/02/2016 11:38 PM, Srikar Dronamraju wrote:
> * Dave Hansen <[email-masked]> [2016-08-02 11:09:21]:
>> On 08/02/2016 06:19 AM, Srikar Dronamraju wrote:
>>> Kernels compiled with CONFIG_DEFERRED_STRUCT_PAGE_INIT will initialise
>>> only certain size memory per node. The certain size takes into account
>>> the dentry and inode cache sizes. However such a kernel when booting a
>>> secondary kernel will not be able to allocate the required amount of
>>> memory to suffice for the dentry and inode caches. This results in
>>> crashes like the below on large systems such as 32 TB systems.
>>
>> What's a "secondary kernel"?
>>
> I mean the kernel thats booted to collect the crash, On fadump, the
> first kernel acts as the secondary kernel i.e the same kernel is booted
> to collect the crash.

OK, but I'm still not seeing what the problem is.  You've said that it
crashes and that it crashes during inode/dentry cache allocation.

But, *why* does the same kernel image crash in when it is used as a
"secondary kernel"?