linux-kernel - Re: parisc DISCONTIGMEM compile breakage

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Date:	Tue, 06 May 2008 17:09:10 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Adrian Bunk <bunk@...nel.org>,
	Christoph Lameter <clameter@....com>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	kyle@...isc-linux.org, matthew@....cx, grundler@...isc-linux.org,
	linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: parisc DISCONTIGMEM compile breakage

On Tue, 2008-05-06 at 22:17 +0100, Mel Gorman wrote:
> On (06/05/08 14:58), James Bottomley didst pronounce:
> > On Tue, 2008-05-06 at 16:27 +0100, Mel Gorman wrote:
> > > On (06/05/08 16:46), Adrian Bunk didst pronounce:
> > > > Commit 54a6eb5c4765aa573a030ceeba2c14e3d2ea5706
> > > > (mm: use two zonelist that are filtered by GFP mask)
> > > > causes the following build error with CONFIG_DISCONTIGMEM=y
> > > > on parisc:
> > > > 
> > > 
> > > Thanks Adrian. I don't have a pa-risc cross-compiler and there isn't one
> > > at the usual source http://userweb.kernel.org/~akpm/cross-compilers but the
> > > patch below should fix it. Note that this debugging code should be deleted if
> > > the mm-initialisation-and-debugging framework in -mm is merged to mainline
> > > as it knows how to print all the zonelists where as the pa-risc equivilant
> > > misses the GFP_THISNODE lists.
> > > 
> > > =====
> > > Subject: [PATCH] Fix pa-risc DISCONTIGMEM compile breakage
> > >     
> > > PA-RISC to aid debugging prints out the zonelists setup by the system. A
> > > bad call to node_zonelist() breaks at compile-time. This patch fixes it.
> > > 
> > > Signed-off-by: Mel Gorman <mel@....ul.ie>
> > > ---
> > >  arch/parisc/mm/init.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
> > > index 1f01284..b0ed709 100644
> > > --- a/arch/parisc/mm/init.c
> > > +++ b/arch/parisc/mm/init.c
> > > @@ -606,7 +606,7 @@ void show_mem(void)
> > >  		int i, j;
> > >  
> > >  		for (i = 0; i < npmem_ranges; i++) {
> > > -			zl = node_zonelist(i);
> > > +			zl = node_zonelist(i, 0);
> > >  			for (j = 0; j < MAX_NR_ZONES; j++) {
> > 
> > This rather doesn't look right.  The intent is for i to iterate over the
> > ranges (as nodes) and j to iterate over the zones to get the zonelist.
> 
> Yes, that appears to be the original intention.
> 
> > The original variable k was going over the mappings, which you replaced
> > with for_each_zone_zonelist.  If you use node_zonelist(i, 0) you don't
> > really look at the actual zones in the map.
> > 
> 
> No, but you filter the one list based on the highest zone that can be
> accesssed.
> 
> > Therefore it seems what will give the original functionality back is
> > actually this:
> > 
> 
> To be fair, a few weeks ago you would have been right. Since then zonelists
> have changed though so that there are only two zonelists per node in
> git-latest. One which is for general allocations and one for GFP_THISNODE. The
> zonelist is filtered based on the GFP flags, hence the iterator. I copied the
> parisc code with the compile-fix into mm/page_alloc.c and called it just to
> be sure and with qemu, I see
> 
> [    0.628960] Zone list for zone 0 on node 0: [0/DMA] 
> [    0.628960] Zone list for zone 1 on node 0: [0/Normal] [0/DMA] 
> [    0.628960] Zone list for zone 2 on node 0: [0/HighMem] [0/Normal] [0/DMA] 
> [    0.628960] Zone list for zone 3 on node 0: [0/Movable] [0/HighMem] [0/Normal] [0/DMA]
> 
> which looks right (movablecore was specified hence the existance of the
> movable zone).

Thanks ... I confirmed that your fix does actually work.  Mysteriously,
this is what it produces as output:

Zone list for zone 0 on node 0: [0/Normal] [0/Normal] 
Zone list for zone 1 on node 0: [0/Normal] [0/Normal] 
Zone list for zone 0 on node 1: [0/Normal] [0/Normal] 
Zone list for zone 1 on node 1: [0/Normal] [0/Normal] 

Which is correct

James


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