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Message-ID: <87y5dhw71o.fsf@xmission.com>
Date:	Thu, 21 Mar 2013 00:22:59 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	vgoyal@...hat.com, cpw@....com, kumagai-atsushi@....nes.nec.co.jp,
	lisa.mitchell@...com, heiko.carstens@...ibm.com,
	akpm@...ux-foundation.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, zhangyanfei@...fujitsu.com
Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement

HATAYAMA Daisuke <d.hatayama@...fujitsu.com> writes:

> OK, rigorously, suceess or faliure of the requested free pages
> allocation depends on actual memory layout at the 2nd kernel boot. To
> increase the possibility of allocating memory, we have no method but
> reserve more memory for the 2nd kernel now.

Good enough.   If there are fragmentation issues that cause allocation
problems on larger boxes we can use vmalloc and remap_vmalloc_range, but
we certainly don't need to start there.

Especialy as for most 8 or 16 core boxes we are talking about a 4KiB or
an 8KiBP allocation.  Aka order 0 or order 1.

Adding more memory is also useful.  It is important in general to keep
the amount of memory needed for the kdump kernel low.

Eric

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