From: Johannes Weiner <hannes@cmpxchg.org>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [patch] vmscan: respect higher order in zone_reclaim()
Date: Wed, 18 Feb 2009 11:26:03 +0100 [thread overview]
Message-ID: <20090218102603.GA2160@cmpxchg.org> (raw)
In-Reply-To: <20090218101204.GA27970@csn.ul.ie>
On Wed, Feb 18, 2009 at 10:12:04AM +0000, Mel Gorman wrote:
> On Tue, Feb 17, 2009 at 08:48:27PM +0100, Johannes Weiner wrote:
> > zone_reclaim() already tries to free the requested 2^order pages but
> > doesn't pass the order information into the inner reclaim code.
> >
> > This prevents lumpy reclaim from happening on higher orders although
> > the caller explicitely asked for that.
> >
> > Fix it up by initializing the order field of the scan control
> > according to the request.
> >
>
> I'm fine with the patch but the changelog could have been better. Optionally
> take this changelog but either way.
>
> Acked-by: Mel Gorman <mel@csn.ul.ie>
>
> Optional alternative changelog
> ==============================
>
> During page allocation, there are two stages of direct reclaim that are applied
> to each zone in the preferred list. The first stage using zone_reclaim()
> reclaims unmapped file backed pages and slab pages if over defined limits as
> these are cheaper to reclaim. The caller specifies the order of the target
> allocation but the scan control is not being correctly initialised.
>
> The impact is that the correct number of pages are being reclaimed but that
> lumpy reclaim is not being applied. This increases the chances of a full
> direct reclaim via try_to_free_pages() is required.
>
> This patch initialises the order field of the scan control as requested
> by the caller.
Agreed, this is better. Thank you, Mel.
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prev parent reply other threads:[~2009-02-18 10:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-17 19:48 Johannes Weiner
2009-02-18 10:12 ` Mel Gorman
2009-02-18 10:26 ` Johannes Weiner [this message]
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