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

[Yinghai Lu <yinghai@kernel.org>]

On Fri, Jun 21, 2013 at 11:44 AM, Greg Kroah-Hartman
<gregkh@linuxfoundation.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@sgi.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