linux-kernel - RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F39F7F4CD@ORSMSX114.amr.corp.intel.com>
Date:	Wed, 9 Dec 2015 21:59:17 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Xishi Qiu <qiuxishi@...wei.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kamezawa.hiroyu@...fujitsu.com" <kamezawa.hiroyu@...fujitsu.com>,
	"mel@....ul.ie" <mel@....ul.ie>,
	"Hansen, Dave" <dave.hansen@...el.com>,
	"matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>
Subject: RE: [PATCH v3 2/2] mm: Introduce kernelcore=mirror option

> How about add some comment, if mirrored memroy is too small, then the
> normal zone is small, so it may be oom.
> The mirrored memory is at least 1/64 of whole memory, because struct
> pages usually take 64 bytes per page.

1/64th is the absolute lower bound (for the page structures as you say). I
expect people will need to configure 10% or more to run any real workloads.

I made the memblock boot time allocator fall back to non-mirrored memory
if mirrored memory ran out.  What happens in the run time allocator if the
non-movable zones run out of pages? Will we allocate kernel pages from movable
memory?

-Tony
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