________________________________
From: Kevin van Kuik [mailto:kkuik@Transfer-Solutions.com]
Sent: 24 August 2006 11:15
To: Petersson, Mats
Subject: RE: [Xen-users] Memory problem''s 2GB mod
If you put 4GB memories (2 X 2GB) xen-3.0.2-2 crashed to and if
when we put 2Gb (2 X 1 GB) it works fine. So 16Gb is not the problem.!
We have tried new memory and we have the same crash.
So if I put 2gb memories it''s crashing with xen-3.0.2-2, but
it''s work fine with redhat 4.1 kernel, xen-3.0.1 So or only explanation
is that xen-3.0.2-2 have a problem with 2 GB memories
I disagree. First and foremost because Xen itself has not knowledge of
what combination of memories (type of module or otherwise) you have.
However, it may EXPOSE some problems that previously didn''t occur, due
to some other scenario... For example, the new version of Xen may have a
different memory access pattern that causes a failure to happen because
there''s some particular sequence of memory accesses, which
doesn''t
happen in the same way with Xen 3.0.1 or plain RedHat. I''ve worked with
hardware long enough to know that "strange things happen" when you mix
different hardware and software.
One thing to consider is to upgrade the BIOS on the machine, just in
case there''s some sort of bug in the memory configuration code in the
BIOS. Here''s how it works: The BIOS recognizes your memory chips (from
the SPD), and then sets up the timing parameters, memory sizing
parameters, number of banks and some other miscellaneous parameters.
Once this setup has been done, nothing touches the memory configuration
registers ever again. Xen has absolutely NO CODE to touch these
registers, so how can Xen itself fail with one memory configuration when
another similar one works - well, because the ORIGINAL setup didn''t
work
right. But it''s not Xen''s fault.
Please feel free to pursue Xen as the culprit if you wish, but I can
100% guarantee you that it''s going to end with you fiinding that
it''s
the memory and/or BIOS and/or motherboard that is ACTUALLY causing the
problem. I know this, because not only have I worked with Xen for the
last year and a bit, but I''ve also written memory sizing/configuration
algorithms for startup of the processor (like what you find in the
BIOS).
Try running Memtest86 on the 2GB memory sticks and see if that shows
anything. That is NOT GUARANTEED to show a problem, but it''s a good
starting point for figuring out that the memory is good or bad.
Just to confirm that software can influence the memory errors, I ran
memtest86 as a HVM instance under Xen - so running the virtual machine
doing memory testing. I got memory errors. I then ran memtest86 on the
machine itself, no errors. Changing to a different memory module (from a
different manufacturer), fixed the problem. It''s still not
Xen''s fault
that the memory fails, it just changes the access pattern by locating
things in a different way, and in the case of HVM models adding memory
mapping to the not-usually-memory-mapped test-case, so there will be a
different memory access pattern when running the HVM guest compared to
running the bare-metal version.
--
Mats
Ragard Kevin
-----Oorspronkelijk bericht-----
Van: Petersson, Mats [mailto:Mats.Petersson@amd.com]
Verzonden: Thursday, August 24, 2006 12:00 PM
Aan: Kevin van Kuik; xen-users@lists.xensource.com
Onderwerp: RE: [Xen-users] Memory problem''s 2GB mod
Xen has absolutely no idea what type of memory modules
you''re using, so obviously this is not DIRECTLY causing the problem.
Have you tried runnign a memory test on the 16GB
memories? It may just be that a slightly different setup of memory
(caused by arbitrary changes in Xen 3.0.1->3.0.2) causes you to hit some
bad spot in the memory.
To utterly prove that it''s not a "module" issue, you
could also try running 4 * 2GB instead of 8 * 1GB, which should have the
same effect.
The only place where the actual configuration of the
memory is known is within the BIOS that sets up the memory configuration
early on in the boot process (before you see any text on your monitor).
Beyond that, no software will touch anything that is related to what
type or model of memory you''re using [except for some utilities that
are
able to READ the memory configuration registers to tell you what type of
memories you''re using, etc, etc].
--
Mats
________________________________
From: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Kevin van
Kuik
Sent: 24 August 2006 00:15
To: xen-users@lists.xensource.com
Subject: [Xen-users] Memory problem''s 2GB mod
I have a HP ml370 with xen-3.0.1 and redhat 4.1
with 16 GB memory (8 x 2GB). I want to upgrade to xen-3.0.2-2 because
the server crashed on the scsi driver.
If I boot the server with xen-3.0.2-2 it crashed
on the boot. But if I put 8 x 1GB memory the server boot fine.
So xen-3.0.2-2 can''t work with 2GB memory
modules. Is there a compile option to solve this problem?
The memory is OK because it''s work fine with
redhat 4.1 (without xen) and xen-3.0.1
regards Kevin
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