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Date: Mon, 13 Jan 2014 16:02:05 +0100
From: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Subject: Re: [PATCH 1/2 V2] raw i/o and root device to use less memory
Message-ID: <20140113160205.6e631a5e@holzheu>
In-Reply-To: <20140113133033.GA917@sgi.com>
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 <20140110175830.GA7498@sgi.com> <20140113105831.57412728@holzheu>
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To: Cliff Wickman <cpw@sgi.com>
Cc: kumagai-atsushi@mxc.nes.nec.co.jp, d.hatayama@jp.fujitsu.com, kexec@lists.infradead.org

On Mon, 13 Jan 2014 07:30:33 -0600
Cliff Wickman <cpw@sgi.com> wrote:

> On Mon, Jan 13, 2014 at 10:58:31AM +0100, Michael Holzheu wrote:
> > On Fri, 10 Jan 2014 11:58:30 -0600
> > Cliff Wickman <cpw@sgi.com> wrote:
> > 
> > [snip]
> > 
> > > Use O_DIRECT (raw) i/o for the dump and for the bitmaps file, so that writing
> > > to those files does not allocate kernel memory for page cache.
> > 
> > Hello Cliff,
> > 
> > Have you tested O_DIRECT together with the new vmcore mmap interface?
> > IIRC when we tried O_DIRECT together with mmap for some reason it did
> > not work.
> > 
> > Michael
> 
> Hi Michael,
> 
>   How new of a kernel do I need?  i.e. how 'new' of an mmap interface?
>   The latest kernel I used was 3.0.93 (sle11sp3).
>   And makedumpfile was 1.5.5.

I think sles11 SP3 does not support mmap for /proc/vmcore. Upstream you
need at least kernel 3.11. For makedumpfile version 1.5.5 should be ok.

Michael


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