linux-kernel - Re: x86/kdump: crashkernel=X try to reserve below 896M first then below 4G and MAXMEM

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Message-ID: <CAE9FiQU+R4Z+3xS9SjUk2i2D8Ht6uhP_pd8maguQOen1UqpgZg@mail.gmail.com>
Date:   Sat, 21 Oct 2017 00:20:33 -0700
From:   Yinghai Lu <yinghai@...nel.org>
To:     Dave Young <dyoung@...hat.com>
Cc:     "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: x86/kdump: crashkernel=X try to reserve below 896M first then
 below 4G and MAXMEM

On Thu, Oct 19, 2017 at 10:52 PM, Dave Young <dyoung@...hat.com> wrote:
> Now crashkernel=X will fail if there's not enough memory at low region
> (below 896M) when trying to reserve large memory size.  One can use
> crashkernel=xM,high to reserve it at high region (>4G) but it is more
> convinient to improve crashkernel=X to:
>
>  - First try to reserve X below 896M (for being compatible with old
>    kexec-tools).
>  - If fails, try to reserve X below 4G (swiotlb need to stay below 4G).
>  - If fails, try to reserve X from MAXMEM top down.
>
> It's more transparent and user-friendly.

ok with me.

But looks like last time Vivek did not like this idea.