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

From: "H. Peter Anvin" <hpa@zytor.com>
To: Nathan Zimmer <nzimmer@sgi.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	holt@sgi.com, travis@sgi.com, rob@landley.net,
	tglx@linutronix.de, mingo@redhat.com, yinghai@kernel.org,
	akpm@linux-foundation.org, x86@kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC 0/2] Delay initializing of large sections of memory
Date: Fri, 21 Jun 2013 10:28:58 -0700	[thread overview]
Message-ID: <51C48D5A.4010602@zytor.com> (raw)
In-Reply-To: <51C48ADD.207@sgi.com>

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