On Sat, 2 Dec 2006, Karsten Weiss wrote:
> On Sat, 2 Dec 2006, Christoph Anton Mitterer wrote:
>
> > I found a severe bug mainly by fortune because it occurs very rarely.
> > My test looks like the following: I have about 30GB of testing data on
>
> This sounds very familiar! One of the Linux compute clusters I
> administer at work is a 336 node system consisting of the
> following components:
>
> * 2x Dual-Core AMD Opteron 275
> * Tyan S2891 mainboard
> * Hitachi HDS728080PLA380 harddisk
> * 4 GB RAM (some nodes have 8 GB) - intensively tested with
> memtest86+
> * SUSE 9.3 x86_64 (kernel 2.6.11.4-21.14-smp) - But I've also
> e.g. tried the latest openSUSE 10.2 RC1+ kernel 2.6.18.2-33 which
> makes no difference.
>
> We are running LS-Dyna on these machines and discovered a
> testcase which shows a similar data corruption. So I can
> confirm that the problem is for real an not a hardware defect
> of a single machine!
Last week we did some more testing with the following result:
We could not reproduce the data corruption anymore if we boot the machines
with the kernel parameter "iommu=soft" i.e. if we use software bounce
buffering instead of the hw-iommu. (As mentioned before, booting with
mem=2g works fine, too, because this disables the iommu altogether.)
I.e. on these systems the data corruption only happens if the hw-iommu
(PCI-GART) of the Opteron CPUs is in use.
Christoph, Erik, Chris: I would appreciate if you would test and hopefully
confirm this workaround, too.
Best regards,
Karsten
--
__________________________________________creating IT solutions
Dipl.-Inf. Karsten Weiss science + computing ag
phone: +49 7071 9457 452 Hagellocher Weg 73
teamline: +49 7071 9457 681 72070 Tuebingen, Germany
email: [email protected] www.science-computing.de
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