linux-kernel - Re: The performance and behaviour of the anti-fragmentation related patches

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Message-ID: <20070302172818.GA15730@skynet.ie>
Date:	Fri, 2 Mar 2007 17:28:18 +0000
From:	mel@...net.ie (Mel Gorman)
To:	Christoph Lameter <clameter@...r.sgi.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, npiggin@...e.de,
	mingo@...e.hu, jschopp@...tin.ibm.com, arjan@...radead.org,
	torvalds@...ux-foundation.org, mbligh@...igh.org,
	kamezawa.hiroyu@...fujitsu.com, linux-kernel@...r.kernel.org
Subject: Re: The performance and behaviour of the anti-fragmentation related patches

On (02/03/07 09:19), Christoph Lameter didst pronounce:
> On Fri, 2 Mar 2007, Mel Gorman wrote:
> 
> > However, if that is objectionable, I'd at least like to see zone-based patches
> > go into -mm on the expectation that the memory hot-remove patches will be
> > able to use the infrastructure. It's not ideal for hugepages and it is not my
> > first preference, but it's a step in the right direction. Is this reasonable?
> 
> I still think that the list based approach is sufficient for memory 
> hotplug if one restricts  the location of the unmovable MAX_ORDER chunks 
> to not overlap the memory area where we would like to be able to remove 
> memory.

Yes, true. In the part where I bias placements of unmovable pages at
lower PFNs, additional steps would need to be taken. Specifically, the
lowest block MAX_ORDER_NR_PAGES used for movable pages would need to be
reclaimed for unmovable allocations.

> In very pressing memory situations where we have too much 
> unmovable memory we could dynamically disable  memory hotplug. There 
> would be no need for this partitioning and additional zones.
> 

It's simply more complex. I believe it's doable. The main plus going for
the zone is that it is a clearly understood concept and it gives hard
guarantees.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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