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

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Message-ID: <51C48D5A.4010602@zytor.com>
Date:	Fri, 21 Jun 2013 10:28:58 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Nathan Zimmer <nzimmer@....com>
CC:	Greg KH <gregkh@...uxfoundation.org>, holt@....com, travis@....com,
	rob@...dley.net, tglx@...utronix.de, mingo@...hat.com,
	yinghai@...nel.org, akpm@...ux-foundation.org, x86@...nel.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/2] Delay initializing of large sections of memory

On 06/21/2013 10:18 AM, Nathan Zimmer wrote:
>>>
>> Since you made it a compile time option, it would be good to know how
>> much code it adds, but otherwise I agree with Greg here... this really
>> shouldn't need to be an option.  It *especially* shouldn't need to be a
>> hand-set runtime option (which looks quite complex, to boot.)
> The patchset as a whole is just over 400 lines so it doesn't add alot.
> If I were to pull the .config option it would probably remove 30 lines.

I'm more concerned about bytes of code.

> The command line option is too complex but some of the data I haven't
> found a way to get at runtime yet.

I think that is probably key.

>> I suspect the cutoff for this should be a lot lower than 8 TB even, more
>> like 128 GB or so.  The only concern is to not set the cutoff so low
>> that we can end up running out of memory or with suboptimal NUMA
>> placement just because of this.
> Even at lower amounts of ram there is an positive impact.I it knocks
> time off
> boot even at as small as a 1TB of ram.

I am not surprised.

	-hpa

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