linux-kernel - Re: [PATCH 03/34] mm: Reduce the amount of work done when updating min_free

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Message-ID: <20120724224712.GB4245@kroah.com>
Date:	Tue, 24 Jul 2012 15:47:12 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Stable <stable@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/34] mm: Reduce the amount of work done when updating
 min_free_kbytes

On Mon, Jul 23, 2012 at 02:38:16PM +0100, Mel Gorman wrote:
> commit 938929f14cb595f43cd1a4e63e22d36cab1e4a1f upstream.
> 
> Stable note: Fixes https://bugzilla.novell.com/show_bug.cgi?id=726210 .
> 	Large machines with 1TB or more of RAM take a long time to boot
> 	without this patch and may spew out soft lockup warnings.

In comparing this with the upstream version, you have a few different
coding style differences, but no real content difference.  Why?

> 
> When min_free_kbytes is updated blocks marked MIGRATE_RESERVE are
> updated. Ordinarily, this work is unnoticable as it happens early
> in boot. However, on large machines with 1TB of memory, this can take
> a considerable time when NUMA distances are taken into account. The bulk
> of the work is done by pageblock_is_reserved() which examines the
> metadata for almost every page in the system. Currently, we are doing
> this far more than necessary as it is only required while there are
> still blocks to be marked MIGRATE_RESERVE. This patch significantly
> reduces the amount of work done by setup_zone_migrate_reserve()
> improving boot times on 1TB machines.
> 
> [akpm@...ux-foundation.org: coding-style fixes]

I'm guessing you didn't pick these up?

Anyway, I've taken it now as the original one from Linus's tree,
hopefully this doesn't burn me later in the series...

thanks,

greg k-h
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