linux-kernel - SLUB doesn't work with kdump kernel on Cell

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Date:	Wed, 08 Aug 2007 17:15:51 -0300
From:	Lucio Correia <ljhc@...ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	Christoph Lameter <clameter@....com>,
	Arnd Bergmann <arndb@...db.de>
Subject: SLUB doesn't work with kdump kernel on Cell

Hi Christoph,

I found a problem with SLUB when trying to boot a kdump kernel on a Cell
QS20 Blade running Fedora 7, kernel 2.6.22.5. If I use SLAB for the
kdump kernel, everything works ok. The fact is that SLUB doesn't find a
page frame for allocation in the current node, due to the flag
GFP_THISNODE on a call to new_slab, and stops at a BUG_ON on line 1802
of slub.c. 

I made a patch (attached) that removes this flag. The kernel passed the
point, booting completely. With 128MB of reserved memory (recommended by
kdump documentation on PPC64), the kdump kernel complains with "Out of
memory" messages during the boot, and also after the boot. With 256MB it
boot fines. 

Also attached is the boot output for 128MB of reserved memory.

I understand that this flag should not be removed, and that there is a
better solution, but it demonstrates the problem. Could you give me some
direction on the better way to solve this problem?

Thanks,

-- 
Lucio Correia
Software Engineer
IBM LTC Brazil

View attachment "slub-kdump-fix.diff" of type "text/x-patch" (525 bytes)

View attachment "KdumpSlubTest20070808-128.txt" of type "text/plain" (20612 bytes)