From: Mel Gorman <mel@csn.ul.ie>
To: Christoph Lameter <cl@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>,
David Rientjes <rientjes@google.com>,
Minchan Kim <minchan.kim@gmail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 05/11] Export unusable free space index via /proc/unusable_index
Date: Tue, 23 Mar 2010 18:14:22 +0000 [thread overview]
Message-ID: <20100323181422.GC5870@csn.ul.ie> (raw)
In-Reply-To: <alpine.DEB.2.00.1003231229310.10178@router.home>
On Tue, Mar 23, 2010 at 12:31:35PM -0500, Christoph Lameter wrote:
> On Tue, 23 Mar 2010, Mel Gorman wrote:
>
> > +/*
> > + * Return an index indicating how much of the available free memory is
> > + * unusable for an allocation of the requested size.
> > + */
> > +static int unusable_free_index(unsigned int order,
> > + struct contig_page_info *info)
> > +{
> > + /* No free memory is interpreted as all free memory is unusable */
> > + if (info->free_pages == 0)
> > + return 1000;
>
>
> Is that assumption correct? If you have no free memory then you do not
> know about the fragmentation status that would result if you would run
> reclaim and free some memory.
True, but reclaim and the freeing of memory is a possible future event.
At the time the index is being measured, saying "there is no free memory" and
"of the free memory available, none if it is usable" has the same end-result -
an allocation attempt will fail so the value makes sense.
If it returned zero, it would be a bit confusing. As memory within the zone
gets consumed, the value for high-orders would go towards 1 until there was
no free memory when it would suddenly go to 0. If you graphed that over
time, it would look a bit strange.
> Going into a compaction mode would not be
> useful. Should this not return 0 to avoid any compaction run when all
> memory is allocated?
>
A combination of watermarks and fragmentation_index is what is used in
the compaction decision, not unusable_free_index.
> Otherwise
>
> Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
>
Thanks
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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next prev parent reply other threads:[~2010-03-23 18:14 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-23 12:25 [PATCH 0/11] Memory Compaction v5 Mel Gorman
2010-03-23 12:25 ` [PATCH 01/11] mm,migration: Take a reference to the anon_vma before migrating Mel Gorman
2010-03-23 12:25 ` [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages Mel Gorman
2010-03-23 17:22 ` Christoph Lameter
2010-03-23 18:04 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 03/11] mm: Share the anon_vma ref counts between KSM and page migration Mel Gorman
2010-03-23 17:25 ` Christoph Lameter
2010-03-23 23:55 ` KAMEZAWA Hiroyuki
2010-03-23 12:25 ` [PATCH 04/11] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA or memory hot-remove Mel Gorman
2010-03-23 12:25 ` [PATCH 05/11] Export unusable free space index via /proc/unusable_index Mel Gorman
2010-03-23 17:31 ` Christoph Lameter
2010-03-23 18:14 ` Mel Gorman [this message]
2010-03-24 0:03 ` KAMEZAWA Hiroyuki
2010-03-24 0:16 ` Minchan Kim
2010-03-24 0:13 ` KAMEZAWA Hiroyuki
2010-03-24 10:25 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 06/11] Export fragmentation index via /proc/extfrag_index Mel Gorman
2010-03-23 17:37 ` Christoph Lameter
2010-03-23 12:25 ` [PATCH 07/11] Memory compaction core Mel Gorman
2010-03-23 17:56 ` Christoph Lameter
2010-03-23 18:15 ` Mel Gorman
2010-03-23 18:33 ` Christoph Lameter
2010-03-23 18:58 ` Mel Gorman
2010-03-23 19:20 ` Christoph Lameter
2010-03-24 1:03 ` KAMEZAWA Hiroyuki
2010-03-24 1:47 ` Minchan Kim
2010-03-24 1:53 ` KAMEZAWA Hiroyuki
2010-03-24 2:10 ` Minchan Kim
2010-03-24 10:57 ` Mel Gorman
2010-03-24 20:33 ` Andrew Morton
2010-03-24 20:59 ` Jonathan Corbet
2010-03-24 21:14 ` Andrew Morton
2010-03-24 21:19 ` Christoph Lameter
2010-03-24 21:19 ` Andrea Arcangeli
2010-03-24 21:28 ` Jonathan Corbet
2010-03-24 21:47 ` Andrea Arcangeli
2010-03-24 21:54 ` Jonathan Corbet
2010-03-24 22:06 ` Andrea Arcangeli
2010-03-24 21:57 ` Andrea Arcangeli
2010-03-25 9:13 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 08/11] Add /proc trigger for memory compaction Mel Gorman
2010-03-23 18:25 ` Christoph Lameter
2010-03-23 18:32 ` Mel Gorman
2010-03-24 20:33 ` Andrew Morton
2010-03-26 10:46 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 09/11] Add /sys trigger for per-node " Mel Gorman
2010-03-23 18:27 ` Christoph Lameter
2010-03-23 22:45 ` Minchan Kim
2010-03-24 0:19 ` KAMEZAWA Hiroyuki
2010-03-23 12:25 ` [PATCH 10/11] Direct compact when a high-order allocation fails Mel Gorman
2010-03-23 23:10 ` Minchan Kim
2010-03-24 11:11 ` Mel Gorman
2010-03-24 11:59 ` Minchan Kim
2010-03-24 12:06 ` Minchan Kim
2010-03-24 12:10 ` Mel Gorman
2010-03-24 12:09 ` Mel Gorman
2010-03-24 12:25 ` Minchan Kim
2010-03-24 1:19 ` KAMEZAWA Hiroyuki
2010-03-24 11:40 ` Mel Gorman
2010-03-25 0:30 ` KAMEZAWA Hiroyuki
2010-03-25 9:48 ` Mel Gorman
2010-03-25 9:50 ` KAMEZAWA Hiroyuki
2010-03-25 10:16 ` Mel Gorman
2010-03-26 1:03 ` KAMEZAWA Hiroyuki
2010-03-26 9:40 ` Mel Gorman
2010-03-24 20:48 ` Andrew Morton
2010-03-25 0:57 ` KAMEZAWA Hiroyuki
2010-03-25 10:21 ` Mel Gorman
2010-03-23 12:25 ` [PATCH 11/11] Do not compact within a preferred zone after a compaction failure Mel Gorman
2010-03-23 18:31 ` Christoph Lameter
2010-03-23 18:39 ` Mel Gorman
2010-03-23 19:27 ` Christoph Lameter
2010-03-24 10:37 ` Mel Gorman
2010-03-24 19:54 ` Christoph Lameter
2010-03-24 20:53 ` Andrew Morton
2010-03-25 9:40 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-03-12 16:41 [PATCH 0/11] Memory Compaction v4 Mel Gorman
2010-03-12 16:41 ` [PATCH 05/11] Export unusable free space index via /proc/unusable_index Mel Gorman
2010-03-15 5:41 ` KAMEZAWA Hiroyuki
2010-03-15 9:48 ` Mel Gorman
2010-03-17 2:42 ` KOSAKI Motohiro
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