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

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Message-ID: <20130311190242.GC12107@redhat.com>
Date:	Mon, 11 Mar 2013 15:02:42 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, 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 Mon, Mar 11, 2013 at 11:46:45AM -0700, H. Peter Anvin wrote:
> On 03/11/2013 11:26 AM, Vivek Goyal wrote:
> >>
> > Hi Yinghai,
> > 
> > In mutt your patches are showing as attachment instead of inline. Mutt
> > thinks attachment is of type "application/octet-stream". Not sure if
> > this is configuration issue on my part or something is going on your
> > end.
> > 
> > I have few more concerns.
> > 
> > - Are we able to reserve 512MB memory now below 896MB. I remember so
> >   far it was broken.
> > 
> 
> What is the purpose of reserving that kind of memory below 896 MB?  If
> you have a 32-bit system, it will likely be useless since you are
> robbing the primary of most of lowmem, on a 64-bit system 896 MB is not
> a magic value in any way...?

Actually I am not sure where did 896MB magic value had come from for
x86_64 so far. I assumed that it was some kexec-tools limitation so
first trying 896MB will preserve working with old kexec-tools. If it
was some kernel limitation, then I agree it should not be required anymore.

I do remember that old pugatory had 2G limit. So may be we can first
try reserve with-in first 2G, then with-in first 4G and then above
4G. (Assuming 896M was not kexec-tools limitation and had something
to do with kernel/initramfs).

Thanks
Vivek
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