Re: [PATCH 2/2] fadump: Disable deferred page struct initialisation

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

* Balbir Singh <bsingharora@gmail.com> [2016-08-03 15:20:42]:

> On Tue, 2016-08-02 at 18:49 +0530, Srikar Dronamraju wrote:
> > Fadump kernel reserves significant number of memory blocks. On a multi-node
> > machine, with CONFIG_DEFFERRED_STRUCT_PAGE support, fadump kernel fails to
> > boot. Fix this by disabling deferred page struct initialisation.
> > 
>
> How much memory does a fadump kernel need? Can we bump up the limits depending
> on the config. I presume when you say fadump kernel you mean kernel with
> FADUMP in the config?

On a regular kernel with CONFIG_FADUMP and fadump configured, 5% of the
total memory is reserved for booting the kernel on crash.  On crash,
fadump kernel reserves the 95% memory and boots into the 5% memory that
was reserved for it. It then parses the reserved 95% memory to collect
the dump.

The problem is not about the amount of memory thats reserved for fadump
kernel. Even if we increase/decrease, we will still end up with the same
issue.

> BTW, I would much rather prefer a config based solution that does not select
> DEFERRED_INIT if FADUMP is enabled.

As Vlastimil rightly pointed out, for fadump, the same kernel is booted
back at a different location when we crash. So we cannot have a config
based solution.

-- 
Thanks and Regards
Srikar Dronamraju

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