linux-kernel - Re: [PATCH] kexec: use Crash kernel for Crash kernel low

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Message-ID: <20130402153957.GG29506@redhat.com>
Date:	Tue, 2 Apr 2013 11:39:57 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, WANG Chao <chaowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kexec: use Crash kernel for Crash kernel low

On Tue, Apr 02, 2013 at 07:45:36AM -0700, Yinghai Lu wrote:

[..]
> 2. keep thing unified when new kexec-tools is used: always high.

I think this is wrong. What if system does not have more than 4G of
memory. crashkernel=x,high will fail. So just because we have new version
of kexec-tools, it does not mean that one can always use crashkernel=x,high.

I think we should do two things.

- Extend crashkernel=X to search for memory below 896M, 4G, MAXMEM in
  that order. To me, this will work best for most of the users.

- For users who really care to not allocate memory in low memory ranges,
  they can use crashkernel=X,high. But even there syntax should be that
  look for memory in higher ranges first otherwise allocate from low
  regions.

  Otherwise it makes life very difficult for a user when there is no
  memory available in higher addresses but it is available in low addresses.
  How does one automate that.

In current form, I double crashkernel=X,high is going to be very useful.

Thanks
Vivek
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