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

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Message-ID: <20130621203337.GA20545@gulag1.americas.sgi.com>
Date:	Fri, 21 Jun 2013 15:33:37 -0500
From:	Nathan Zimmer <nzimmer@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Nathan Zimmer <nzimmer@....com>,
	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 Fri, Jun 21, 2013 at 01:08:06PM -0700, H. Peter Anvin wrote:
> Is this init code?  32K of unconditional runtime addition isn't completely trivial.

Some of it is init code but not all.
I am guessing 24k of that is actually runtime.

> 
> Nathan Zimmer <nzimmer@....com> wrote:
> 
> >On 06/21/2013 12:28 PM, H. Peter Anvin wrote:
> >> 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.
> >Oh, The difference is just under 32k.
> >371843425 Jun 21 14:08 vmlinux.o /* DELAY_MEM_INIT is not set  */
> >371875600 Jun 21 14:36 vmlinux.o /* DELAY_MEM_INIT=y */
> >
> >>
> >>> 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
> >>
> 
> -- 
> Sent from my mobile phone. Please excuse brevity and lack of formatting.
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