linux-kernel - Re: [PATCH 1/3] clean up setup_per_zone_pages

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Date:	Wed, 20 May 2009 19:30:45 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Minchan Kim <minchan.kim@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 1/3] clean up setup_per_zone_pages_min

On Wed, 20 May 2009 11:21:29 +0100
Mel Gorman <mel@....ul.ie> wrote:

> On Wed, May 20, 2009 at 06:58:03PM +0900, Minchan Kim wrote:
> > Hi, Mel. 
> > 
> > On Wed, 20 May 2009 09:54:16 +0100
> > Mel Gorman <mel@....ul.ie> wrote:
> > 
> > > On Wed, May 20, 2009 at 04:18:53PM +0900, Minchan Kim wrote:
> > > > 
> > > > Mel changed zone->pages_[high/low/min] with zone->watermark array.
> > > > So, setup_per_zone_pages_min also have to be changed.
> > > > 
> > > 
> > > Just to be clear, this is a function renaming to match the new zone
> > > field name, not something I missed. As the function changes min, low and
> > > max, a better name might have been setup_per_zone_watermarks but whether
> > 
> > At first, I thouht, too. But It's handle of min_free_kbytes.
> > Documentation said, it's to compute a watermark[WMARK_MIN]. 
> > I think many people already used that knob to contorl pages_min to keep the 
> > low pages. 
> 
> Which documentation?

Documentation/sysctl/vm.txt - min_free_kbytes.

> I'm looking at the function comment and see
> 
>  * setup_per_zone_pages_min - called when min_free_kbytes changes.
>  *
>  * Ensures that the pages_{min,low,high} values for each zone are set
>  * correctly with respect to min_free_kbytes.
> 
> So, the values of all the watermarks are updated by that function depending
> on what the new value of min_free_kbytes is. It is a bit wrong I suppose as
> it missed memory hot-add
> 
> setup_per_zone_pages_min - called when min_free_kbytes changes or when memory is hot-added

God!. I changed this function's comments with memory hot plug. 
With my mistake, My patch 3/3 lost it. 
I will add comment about memory hotplug.

Thanks for pointing me out. :)


> > 
> > So, I determined function name is proper now. 
> > If setup_per_zone_watermark is better than it, we also have to change with 
> > documentation. 
> > 
> > > you go with that name or not, this is better than what is there so;
> > > 
> > > Acked-by: Mel Gorman <mel@....ul.ie>
> > 
> > 
> > -- 
> > Kinds Regards
> > Minchan Kim
> > 
> 
> -- 
> Mel Gorman
> Part-time Phd Student                          Linux Technology Center
> University of Limerick                         IBM Dublin Software Lab


-- 
Kinds Regards
Minchan Kim
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