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

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Message-ID: <CAE9FiQUfL9695iDY6zMwA5j6OGL8edotXwfSNBHsHC54qqEAGQ@mail.gmail.com>
Date:	Fri, 21 Jun 2013 12:00:44 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Nathan Zimmer <nzimmer@....com>, Robin Holt <holt@....com>,
	Mike Travis <travis@....com>, Rob Landley <rob@...dley.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	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 Fri, Jun 21, 2013 at 11:44 AM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Fri, Jun 21, 2013 at 11:36:21AM -0700, Yinghai Lu wrote:
>> On Fri, Jun 21, 2013 at 9:25 AM, Nathan Zimmer <nzimmer@....com> wrote:
>> > This rfc patch set delays initializing large sections of memory until we have
>> > started cpus.  This has the effect of reducing startup times on large memory
>> > systems.  On 16TB it can take over an hour to boot and most of that time
>> > is spent initializing memory.
>>
>> One hour on system with 16T ram? BIOS or OS?
>>
>> I use wall clock to check bootime on one system with 3T and 16 pcie cards,
>> Linus only takes about 3m and 30 seconds from bootloader.
>>
>> wonder if you boot delay is with so many cpu get onlined in serialized mode.
>>
>> so can you try boot your system with "maxcpus=128" to get the boot time with
>> wall clock ?
>
> Why use the "wall clock" when we have the wonderful bootchart tools and
> scripts that do this all for you, and can tell you exactly what part of
> the kernel is taking what time, to help with fixing issues like this?

bootchart is not completed.

printk timestamp come after mem get initialized.
....
[    0.004000] tsc: Fast TSC calibration using PIT

before that stamp are all 0.

Yinghai
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