From: Mel Gorman <mgorman@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm: Reduce the amount of work done when updating min_free_kbytes
Date: Tue, 15 Nov 2011 12:23:15 +0000 [thread overview]
Message-ID: <20111115122315.GD27150@suse.de> (raw)
In-Reply-To: <20111114152100.1333a015.akpm@linux-foundation.org>
On Mon, Nov 14, 2011 at 03:21:00PM -0800, Andrew Morton wrote:
> On Fri, 11 Nov 2011 16:21:19 +0000
> Mel Gorman <mgorman@suse.de> wrote:
>
> > When min_free_kbytes is updated, some pageblocks are marked MIGRATE_RESERVE.
> > Ordinarily, this work is unnoticable as it happens early in boot but on
> > large machines with 1TB of memory, this has been reported to delay
> > boot times, probably due to the NUMA distances involved.
> >
> > The bulk of the work is due to calling calling pageblock_is_reserved()
> > an unnecessary amount of times and accessing far more struct page
> > metadata than is necessary. This patch significantly reduces the
> > amount of work done by setup_zone_migrate_reserve() improving boot
> > times on 1TB machines.
> >
>
> By how much? :)
>
> (I mainly ask because I'm curious to know how long the kernel takes to
> boot on a 1TB machine...)
>
Good question. I don't have access to the machine but based on the dmesg
they posted before and after, this patch reduced boot times by 27
seconds.
With only dmesg, I don't know how long it is taking to start services
and mount of the filesystem but assuming no major problems or timeouts
from drivers it looks like it is taking about 6 minutes to boot.
--
Mel Gorman
SUSE Labs
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prev parent reply other threads:[~2011-11-15 12:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-11 16:21 [PATCH] mm: Reduce the amount of work done when updating min_free_kbytes Mel Gorman
2011-11-14 23:21 ` Andrew Morton
2011-11-15 12:23 ` Mel Gorman [this message]
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