linux-kernel - Re: [PATCH] x86, kdump: Set crashkernel

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Message-ID: <513E4064.7090501@zytor.com>
Date:	Mon, 11 Mar 2013 13:36:52 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	WANG Chao <chaowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86, kdump: Set crashkernel_low automatically

On 03/11/2013 01:19 PM, H. Peter Anvin wrote:
> 
> The problem with this argument here is that we are spiraling down the
> drain of increasing user-visible complexity in order to not break
> existing but exotic use cases.  We need to stop and reverse this trend.
>  I want to make a few observations on this:
> 
> 1. Running with an archaic kexec-tools should be considered an anomaly.
>  If necessary, we could introduce a kernel option to let the kernel know
> which kexec-tools version the user will use.
> 
> 2. As long as memory is available, there is always the option to shift
> memory around to accommodate the crashkernel.  That probably should have
> been done all along.
> 
> 3. The memory size reserved should be deduced automatically to the
> greatest possible extent.
> 

The really big picture problem here is that the host kernel is expected
to predict at boot time what will happen in the future: what are the
requirements of the kdump kernel, and its tools, which hasn't been
loaded yet?

Can we get past that as a fundamental problem?

	-hpa

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