linux-kernel - Re: [RFC 0/2] Delay initializing of large sections of memory

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Message-ID: <51C9EADD.5000904@zytor.com>
Date:	Tue, 25 Jun 2013 12:09:17 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Mike Travis <travis@....com>, Ingo Molnar <mingo@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Nathan Zimmer <nzimmer@....com>, Robin Holt <holt@....com>,
	Rob Landley <rob@...dley.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	linux-doc@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 0/2] Delay initializing of large sections of memory

On 06/25/2013 12:03 PM, Yinghai Lu wrote:
>> It is worth experimenting with but the big question would be,
>> if it still avoids the very expensive "memmap_init_zone" and
>> it's sub-functions using huge expanses of memory.  I'll do some
>> experimenting as soon as I can.  Our 32TB system is being
>> brought back to 16TB (we found a number of problems as we
>> get closer and closer to the 64TB limit), but that's still
>> a significant size.
> 
> According to Intel SDM, CPU could support 52bits physical addressing.
> 
> So how linux kernel will handle it? as we only have 48bits virtual addressing.
> 

The Linux kernel will not support more than V-2 bits of physical address
space for any number V of virtual address bits.

	-hpa


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