From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dan Magenheimer <dan.magenheimer@oracle.com>
Subject: RE: Memory fragmentation, order>0 allocation,
 and 4.0 dynamic RAM optimization features
Date: Thu, 18 Feb 2010 08:09:38 -0800 (PST)
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To: Jan Beulich <JBeulich@novell.com>
Cc: xen-devel@lists.xensource.com, Tim Deegan <Tim.Deegan@citrix.com>, GeorgeDunlap <george.dunlap@eu.citrix.com>, PatrickColp <pjcolp@cs.ubc.ca>, Ian Pratt <Ian.Pratt@eu.citrix.com>, Andrew Peace <Andrew.Peace@eu.citrix.com>, Keir Fraser <keir.fraser@eu.citrix.com>, Grzegorz Milos <gm281@cam.ac.uk>
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> From: Jan Beulich [mailto:JBeulich@novell.com]
> >>> Dan Magenheimer <dan.magenheimer@oracle.com> 08.02.10 19:13 >>>
> >Are there other known order>0 allocations that might result
> >in similar issues?
>=20
> Interestingly, tmem itself indirectly causes order-1 allocations
> (through
> the use of xmem_pool_create(), sizeof(struct xmem_pool) =3D 0x18d0
> on a non-debug build).

Well that's embarrassing :-}

But to be fair:
1) tmem is just using xen infrastructure code that suffers from the
   same pervasive problem (though admittedly I added the interface
   to xmalloc_tlsf to enable additional xmem pools to be created)
2) tmem fails semi-gracefully by just turning itself off for
   a domain that fails this order-1 allocation (though it really
   need only disable persistent pools, not all tmem pools)

But ignoring my flimsy excuses, Jan, do you have some debug code
you are using to identify order>0 allocations?  If so, could I
have a copy... and perhaps Keir would consider adding
it post-4.0 to make it easier to search-and-destroy.