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

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Message-ID: <CAOJsxLG0Tr2QV8P55vJDOeUPoWw8xBextQ-qzj4E+PnOk9JBsQ@mail.gmail.com>
Date:	Tue, 28 Apr 2015 19:06:04 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nathan Zimmer <nzimmer@....com>,
	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 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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