linux-kernel - Re: [PATCH] x86, kdump: crashkernel=X try to reserve below 896M first, then try below 4G, then MAXMEM

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Message-ID: <20131024191821.GE2322@redhat.com>
Date:	Thu, 24 Oct 2013 15:18:21 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	WANG Chao <chaowang@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Pekka Enberg <penberg@...nel.org>,
	Jacob Shin <jacob.shin@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86, kdump: crashkernel=X try to reserve below 896M
 first, then try below 4G, then MAXMEM

On Thu, Oct 24, 2013 at 12:15:25PM -0700, Yinghai Lu wrote:
> On Thu, Oct 24, 2013 at 7:02 AM, Vivek Goyal <vgoyal@...hat.com> wrote:
> > On Wed, Oct 23, 2013 at 11:11:51PM -0700, Yinghai Lu wrote:
> >
> > Hence both crashkernel=xM and crashkernel=XM,high have their own usage.
> > We have been using crashkernel=xM and we know it works. So extending it
> > to be able to allocate memory from higher regions, if sufficient memory
> > is not available in lower regions makes sense. Memory reservation below
> > 4G is more efficient due to not requiring swiotlb. And crashkernel=xM
> > has been working for us and users are familiar with it.
> >
> > So I don't see a point that why would you try to block any move to
> > extend crashkernel=xM semantics.
> 
> Make the thing simple.
> Keep them separately, leave crashkernel=xM to old kexec-tools mostly
> and keep crashkernel=xM,high to newer kexec-tools as needed.

I am keeping things simple by making sure that both old kexec-tools and
new kexec-tools can use crashkernel=xM and one does not have to choose
between two based on what kexec-tools version you are using.

Also keeping things simple by not trying to *impose* a new crashkernel=
syntax on existing crashkernel=xM users.

Hence extending the semantics of crashkernel=xM makes sense to me.

Thanks
Vivek
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