linux-kernel - Re: [PATCH 0/13] Parallel struct page initialisation v4

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Date:	Tue, 28 Apr 2015 13:38:20 -0500
From:	nzimmer <nzimmer@....com>
To:	Pekka Enberg <penberg@...nel.org>, Mel Gorman <mgorman@...e.de>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Waiman Long <waiman.long@...com>,
	Scott Norton <scott.norton@...com>,
	Daniel J Blueman <daniel@...ascale.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/13] Parallel struct page initialisation v4

On an older 8 TB box with lots and lots of cpus the boot time, as 
measure from grub to login prompt, the boot time improved from 1484 
seconds to exactly 1000 seconds.

I have time on 16 TB box tonight and a 12 TB box thursday and will 
hopefully have more numbers then.



On 04/28/2015 11:06 AM, Pekka Enberg wrote:
> On Tue, Apr 28, 2015 at 5:36 PM, Mel Gorman <mgorman@...e.de> wrote:
>> Struct page initialisation had been identified as one of the reasons why
>> large machines take a long time to boot. Patches were posted a long time ago
>> to defer initialisation until they were first used.  This was rejected on
>> the grounds it should not be necessary to hurt the fast paths. This series
>> reuses much of the work from that time but defers the initialisation of
>> memory to kswapd so that one thread per node initialises memory local to
>> that node.
>>
>> After applying the series and setting the appropriate Kconfig variable I
>> see this in the boot log on a 64G machine
>>
>> [    7.383764] kswapd 0 initialised deferred memory in 188ms
>> [    7.404253] kswapd 1 initialised deferred memory in 208ms
>> [    7.411044] kswapd 3 initialised deferred memory in 216ms
>> [    7.411551] kswapd 2 initialised deferred memory in 216ms
>>
>> On a 1TB machine, I see
>>
>> [    8.406511] kswapd 3 initialised deferred memory in 1116ms
>> [    8.428518] kswapd 1 initialised deferred memory in 1140ms
>> [    8.435977] kswapd 0 initialised deferred memory in 1148ms
>> [    8.437416] kswapd 2 initialised deferred memory in 1148ms
>>
>> Once booted the machine appears to work as normal. Boot times were measured
>> from the time shutdown was called until ssh was available again.  In the
>> 64G case, the boot time savings are negligible. On the 1TB machine, the
>> savings were 16 seconds.
> FWIW,
>
> Acked-by: Pekka Enberg <penberg@...nel.org>
>
> for the whole series.
>
> - Pekka

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