Re: [PATCH/RFC 0/5] Memory Policy Cleanups and Enhancements

[Mel Gorman <mel@csn.ul.ie>]

On Fri, 2007-09-14 at 11:06 -0400, Lee Schermerhorn wrote:
> On Fri, 2007-09-14 at 09:53 +0100, Mel Gorman wrote:
> > On (13/09/07 14:17), Andrew Morton didst pronounce:
> > > On Thu, 13 Sep 2007 11:26:19 -0700 (PDT)
> > > Christoph Lameter <clameter@sgi.com> wrote:
> > > 
> > > > On Thu, 13 Sep 2007, Mel Gorman wrote:
> > > > 
> > > > > What do you see holding it up? Is it the fact we are no longer doing the
> > > > > pointer packing and you don't want that structure to exist, or is it simply
> > > > > a case that 2.6.23 is too close the door and it won't get adequate
> > > > > coverage in -mm?
> > > > 
> > > > No its not the pointer packing. The problem is that the patches have not 
> > > > been merged yet and 2.6.23 is close. We would need to merge it very soon 
> > > > and get some exposure in mm. Andrew?
> > > 
> > > You rang?
> > > 
> > > To which patches do you refer?  "Memory Policy Cleanups and Enhancements"? 
> > > That's still in my queue somewhere, but a) it has "RFC" in it which usually
> > > makes me run away and b) we already have no fewer than 221 memory
> > > management patches queued.
> > > 
> > 
> > Christoph's question is in relation to the patchset "Use one zonelist per
> > node instead of multiple zonelists v7" and whether one zonelist will be
> > merged in 2.6.24 in your opinion. I am hoping "yes" because it removes that
> > hack with ZONE_MOVABLE and policies. I had sent you a version (v5) but there
> > were further suggestions on ways to improve it so we're up to v7 now. Lee
> > will hopefully be able to determine if v7 regresses policy behaviour or not.
> > 
> 
> Hi, Mel:
> 
> I'm running with your patches now.  An earlier version--just received v7
> end of day yesterday.  Will rebuild today.  I've been using the kernel
> with your patches for general patch development and kernel building on
> my ia64 numa platform.  Before I rebooted to test another kernel
> [reclaim scalability/noreclaim patch set], your mail prompted me to try
> a couple of memtoy migration scripts.  I managed to hang/panic the
> system with a null pointer deref and a very interesting stack trace,
> which I didn't capture [want to test w/ v7]. 

Very uncool. If I am null dereferencing anywhere, it's going to be in
the iterator so check for get_page_from_freelist() in the stack.

>  The trace included some
> kprobes functions--which I'm not using--and a lot of tcp/network stack
> routines.  I have no clue whether these are related to your patches.
> The hang that I experienced before the panic could have been a local
> site network glitch [happens, sometimes] that triggered a fault in the
> network stack.
> 

How bizarre.

> Again, I'll retest with the v7 patches today.  In the meantime, you
> might want to grab memtoy from:
> http://free.linux.hp.com/~lts/Tools/memtoy-latest.tar.gz
> and try out the test scripts in the Xpm-tests/Mbind directory.  Note
> that these scripts assume a 4-node numa system, but from the comments
> you should be able to mod them for whatever numa system you have
> available.  Building memtoy can also be a bit of a challenge, depending
> on your environment--no autoconfig or such.  Check out the README for
> instructions/caveats/...
> 

Ok, I'll give it a shot and see how I get on. Thanks Lee

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