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[Xen-devel] RE: Memory fragmentation, order>0 allocation, and 4.0 dynami

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: [Xen-devel] RE: Memory fragmentation, order>0 allocation, and 4.0 dynamic RAM optimization features
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Thu, 18 Feb 2010 09:32:05 -0800 (PST)
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Tim Deegan <Tim.Deegan@xxxxxxxxxx>, GeorgeDunlap <george.dunlap@xxxxxxxxxxxxx>, PatrickColp <pjcolp@xxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, Andrew Peace <Andrew.Peace@xxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, Grzegorz Milos <gm281@xxxxxxxxx>
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> Since you are so eager to point out and fix all order > 0 allocations

"eager" is a rather poor word choice :-)

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxxxx]
> Sent: Thursday, February 18, 2010 9:19 AM
> To: Dan Magenheimer
> Cc: Grzegorz Milos; Tim Deegan; PatrickColp; Andrew Peace;
> GeorgeDunlap; Ian Pratt; Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: Memory fragmentation, order>0 allocation, and 4.0 dynamic
> RAM optimization features
> 
> >>> Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> 18.02.10 17:09 >>>
> >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.
> 
> I actually noticed this only as a side effect from a much uglier
> debugging
> patch - observing apparent memory corruption with no apparent pattern
> during save/restore/migrate, I finally decided to try a brute force
> method
> and track all allocations. Since you are so eager to point out and fix
> all
> order > 0 allocations, I was quite surprised to see one while tmem
> itself initialized its state for Dom0. Hence I thought I'd point it
> out. The
> patch as it stands is, I think, not really a general debugging aid - if
> you
> think differently, I can of course still share it.
> 
> Jan
> 

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