Message-ID: <51C9E4B7.2000007@zytor.com>
Date: Tue, 25 Jun 2013 11:43:03 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Mike Travis <travis@sgi.com>
CC: Ingo Molnar <mingo@kernel.org>, Nathan Zimmer <nzimmer@sgi.com>,
        holt@sgi.com, rob@landley.net, tglx@linutronix.de, mingo@redhat.com,
        yinghai@kernel.org, akpm@linux-foundation.org,
        gregkh@linuxfoundation.org, x86@kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [RFC 2/2] x86_64, mm: Reinsert the absent memory
References: <1371831934-156971-1-git-send-email-nzimmer@sgi.com> <1371831934-156971-3-git-send-email-nzimmer@sgi.com> <20130623092840.GB13445@gmail.com> <20130624203657.GA107621@asylum.americas.sgi.com> <20130625073819.GC11420@gmail.com> <51C9D1D6.20405@sgi.com>
In-Reply-To: <51C9D1D6.20405@sgi.com>
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On 06/25/2013 10:22 AM, Mike Travis wrote:
> 
> On 6/25/2013 12:38 AM, Ingo Molnar wrote:
>>
>> * Nathan Zimmer <nzimmer@sgi.com> wrote:
>>
>>> On Sun, Jun 23, 2013 at 11:28:40AM +0200, Ingo Molnar wrote:
>>>>
>>>> That's 4.5 GB/sec initialization speed - that feels a bit slow and the 
>>>> boot time effect should be felt on smaller 'a couple of gigabytes' 
>>>> desktop boxes as well. Do we know exactly where the 2 hours of boot 
>>>> time on a 32 TB system is spent?
>>>
>>> There are other several spots that could be improved on a large system 
>>> but memory initialization is by far the biggest.
>>
>> My feeling is that deferred/on-demand initialization triggered from the 
>> buddy allocator is the better long term solution.
> 
> I haven't caught up with all of Nathan's changes yet (just
> got back from vacation), but there was an option to either
> start the memory insertion on boot, or trigger it later
> using the /sys/.../memory interface.  There is also a monitor
> program that calculates the memory insertion rate.  This was
> extremely useful to determine how changes in the kernel
> affected the rate.
> 

Sorry, I *totally* did not follow that comment.  It seemed like a
complete non-sequitur?

	-hpa


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