Xen devel - Jan 2008 - Re: Massive problems with ''PCI-DMA: Out of SW-IOMMU space for XXX bytes [..]'' with 3Ware controller

Markus Schuster wrote:
> PCI-DMA: Out of SW-IOMMU space for 40960 bytes at device 0000:03:00.0
> 3w-9xxx: scsi0: ERROR: (0x06:0x001C): Failed to map scatter gather list.
> (03:00.0 is the 3Ware Controller)
Me too as well...any progress on this issue?

I notice that IO performance is notably slower than the stock RHEL kernel; 
about 1/2 overall write performance.  I can trigger the bug using DD or by 
copying disk images around.  All versions of Xen 3.1.x and 3.2.x are 
affected.

-- 
Randy McAnally
Fast Serv Networks, LLC
619-819-8252 x201
619-819-9443 fax


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Randy McAnally wrote:
>> PCI-DMA: Out of SW-IOMMU space for 40960 bytes at device 0000:03:00.0
>> 3w-9xxx: scsi0: ERROR: (0x06:0x001C): Failed to map scatter gather
list.
>> (03:00.0 is the 3Ware Controller)
> 
> Me too as well...any progress on this issue?
I thought about writing to the mailing-list this days, too. Maybe there has
been some fix in 3.2.0 or 3.1.3?
Keir, do you have any news on this annoying issue?

Regards, Markus


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On 28/1/08 21:33, "Markus Schuster" <ma.schuster@gmx.de> wrote:
> Randy McAnally wrote:
>>> PCI-DMA: Out of SW-IOMMU space for 40960 bytes at device
0000:03:00.0
>>> 3w-9xxx: scsi0: ERROR: (0x06:0x001C): Failed to map scatter gather
list.
>>> (03:00.0 is the 3Ware Controller)
>> 
>> Me too as well...any progress on this issue?
> 
> I thought about writing to the mailing-list this days, too. Maybe there has
> been some fix in 3.2.0 or 3.1.3?
> Keir, do you have any news on this annoying issue?
No, except to say that it is almost certainly a dom0 kernel issue, not core
hypervisor. So it will not be fixed by just changing hypervisor version if
you retain the same dom0 kernel version. What kernel are you using? Have you
tried a vendor Xen kernel for your distro?

I think there have been reports of this problem with our 2.6.18-based
kernel, but noone has provided a patch to fix it as far as I know.

 -- Keir



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Keir Fraser wrote:
> No, except to say that it is almost certainly a dom0 kernel issue, not
> core hypervisor. 
I agree on this. 

> So it will not be fixed by just changing hypervisor 
> version if you retain the same dom0 kernel version. 
I agree on this, too. My tests showed that you are right with your
assumption so far.
But i would have used the matching kernel patch, too. 

> What kernel are you using? 
I''ve tried Debians 2.6.18 patched for XEN 3.1.2 myself.

> Have you tried a vendor Xen kernel for your distro? 
That''s the last thing I wanted to try but couldn''t find time
to reboot the
affected server to test it out. My intention was not to use a distro
kernel, as Debians 2.6.18 is patched for XEN 3.0.3. I could stay with my
current 3.0.4 system and I would be more recent. 

Regards, 
Markus


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On 29/1/08 22:38, "Markus Schuster" <ma.schuster@gmx.de> wrote:
>> What kernel are you using?
> 
> I''ve tried Debians 2.6.18 patched for XEN 3.1.2 myself.
> 
> 
>> Have you tried a vendor Xen kernel for your distro?
> 
> That''s the last thing I wanted to try but couldn''t find
time to reboot the
> affected server to test it out. My intention was not to use a distro
> kernel, as Debians 2.6.18 is patched for XEN 3.0.3. I could stay with my
> current 3.0.4 system and I would be more recent.
Can you try our more up-to-date Linux kernel at:
 http://xenbits.xensource.com/linux-2.6.18-xen.hg

Yes, you have to pull it from mercurial and configure and build it yourself,
I''m afraid. But it would be useful to know whether this is something we
have
fixed (knowingly or not) and simply not yet backported to 3.1 branch.

 -- Keir



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Keir Fraser wrote:
>>> Have you tried a vendor Xen kernel for your distro?
>> 
>> That''s the last thing I wanted to try but couldn''t
find time to reboot
>> the affected server to test it out. My intention was not to use a
distro
>> kernel, as Debians 2.6.18 is patched for XEN 3.0.3. I could stay with
my
>> current 3.0.4 system and I would be more recent.
> 
> Can you try our more up-to-date Linux kernel at:
>  http://xenbits.xensource.com/linux-2.6.18-xen.hg
> 
> Yes, you have to pull it from mercurial and configure and build it
> yourself, I''m afraid. But it would be useful to know whether this
is
> something we have fixed (knowingly or not) and simply not yet backported
> to 3.1 branch.
That''s not the problem. I''m able to check out mercurial and
compile my own
kernel from the source. Major problem is free time - you will know :)
But I will try if time permits. 

Regards, Markus


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