linux-kernel - RE: [PATCH] mm: Introduce kernelcore=reliable option

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Date:	Tue, 20 Oct 2015 00:34:51 +0000
From:	"Izumi, Taku" <izumi.taku@...fujitsu.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"tony.luck@...el.com" <tony.luck@...el.com>,
	"Kamezawa, Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"mel@....ul.ie" <mel@....ul.ie>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"dave.hansen@...el.com" <dave.hansen@...el.com>,
	"matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>
Subject: RE: [PATCH] mm: Introduce kernelcore=reliable option

 Hi Xishi,

> On 2015/10/15 21:32, Taku Izumi wrote:
> 
> > Xeon E7 v3 based systems supports Address Range Mirroring
> > and UEFI BIOS complied with UEFI spec 2.5 can notify which
> > ranges are reliable (mirrored) via EFI memory map.
> > Now Linux kernel utilize its information and allocates
> > boot time memory from reliable region.
> >
> > My requirement is:
> >   - allocate kernel memory from reliable region
> >   - allocate user memory from non-reliable region
> >
> > In order to meet my requirement, ZONE_MOVABLE is useful.
> > By arranging non-reliable range into ZONE_MOVABLE,
> > reliable memory is only used for kernel allocations.
> >
> > This patch extends existing "kernelcore" option and
> > introduces kernelcore=reliable option. By specifying
> > "reliable" instead of specifying the amount of memory,
> > non-reliable region will be arranged into ZONE_MOVABLE.
> >
> > Earlier discussion is at:
> >  https://lkml.org/lkml/2015/10/9/24
> >
> 
> Hi Taku,
> 
> If user don't want to waste a lot of memory, and he only set
> a few memory to mirrored memory, then the kernelcore is very
> small, right? That means OS will have a very small normal zone
> and a very large movable zone.

 Right.

> Kernel allocation could only use the unmovable zone. As the
> normal zone is very small, the kernel allocation maybe OOM,
> right?

 Right.

> Do you mean that we will reuse the movable zone in short-term
> solution and create a new zone(mirrored zone) in future?

 If there is that kind of requirements, I don't oppose 
 creating a new zone.

 Sincerely,
 Taku Izumi
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