linux-kernel - Re: [PATCH 0/3] makedumpfile: hugepage filtering for vmcore dump

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Date:	Tue, 5 Nov 2013 20:53:14 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Jingbai Ma <jingbai.ma@...com>
Cc:	ptesarik@...e.cz, d.hatayama@...fujitsu.com,
	kumagai-atsushi@....nes.nec.co.jp, bhe@...hat.com,
	tom.vaden@...com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, lisa.mitchell@...com,
	anderson@...hat.com, ebiederm@...ssion.com
Subject: Re: [PATCH 0/3] makedumpfile: hugepage filtering for vmcore dump

On Wed, Nov 06, 2013 at 09:47:49AM +0800, Jingbai Ma wrote:
> On 11/06/2013 04:26 AM, Vivek Goyal wrote:
> >On Tue, Nov 05, 2013 at 09:45:32PM +0800, Jingbai Ma wrote:
> >>This patch set intend to exclude unnecessary hugepages from vmcore dump file.
> >>
> >>This patch requires the kernel patch to export necessary data structures into
> >>vmcore: "kexec: export hugepage data structure into vmcoreinfo"
> >>http://lists.infradead.org/pipermail/kexec/2013-November/009997.html
> >>
> >>This patch introduce two new dump levels 32 and 64 to exclude all unused and
> >>active hugepages. The level to exclude all unnecessary pages will be 127 now.
> >
> >Interesting. Why hugepages should be treated any differentely than normal
> >pages?
> >
> >If user asked to filter out free page, then it should be filtered and
> >it should not matter whether it is a huge page or not?
> 
> Yes, free hugepages should be filtered out with other free pages. It
> sounds reasonable.
> 
> But for active hugepages, I would offer user more
> choices/flexibility. (maybe bad).
> I'm OK to filter active hugepages with other user data page.
> 
> Any other comments?

I really can't see why hugepages are different than regular pages when
it comes to filtering. IMO, we really should not create filtering
option/levels only for huge pages, until and unless there is a strong
use case.

Thanks
Vivek
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