Re: [RFC v8 PATCH 00/20] memory-hotplug: hot-remove physical memory

At 09/13/2012 01:18 AM, Vasilis Liaskovitis Wrote:

Hi,

On Wed, Sep 12, 2012 at 01:20:28PM +0800, Wen Congyang wrote:

quoted

quoted

On Mon, Sep 10, 2012 at 10:01:44AM +0800, Wen Congyang wrote:

quoted

At 09/10/2012 09:46 AM, Yasuaki Ishimatsu Wrote:

quoted

How do you test the patch? As Andrew says, for hot-removing memory,
we need a particular hardware. I think so too. So many people may want
to know how to test the patch.
If we apply following patch to kvm guest, can we hot-remove memory on
kvm guest?

http://lists.gnu.org/archive/html/qemu-devel/2012-07/msg01389.html

Yes, if we apply this patchset, we can test hot-remove memory on kvm guest.
But that patchset doesn't implement _PS3, so there is some restriction.

the following repos contain the patchset above, plus 2 more patches that add
PS3 support to the dimm devices in qemu/seabios:

https://github.com/vliaskov/seabios/commits/memhp-v2
https://github.com/vliaskov/qemu-kvm/commits/memhp-v2

I have not posted the PS3 patches yet in the qemu list, but will post them
soon for v3 of the memory hotplug series. If you have issues testing, let me
know.

Hmm, seabios doesn't support ACPI table SLIT. We can specify node it for dimm
device, so I think we should support SLIT in seabios. Otherwise we may meet
the following kernel messages:
[  325.016769] init_memory_mapping: [mem 0x40000000-0x5fffffff]
[  325.018060]  [mem 0x40000000-0x5fffffff] page 2M
[  325.019168] [ffffea0001000000-ffffea00011fffff] potential offnode page_structs
[  325.024172] [ffffea0001200000-ffffea00013fffff] potential offnode page_structs
[  325.028596]  [ffffea0001400000-ffffea00017fffff] PMD -> [ffff880035000000-ffff8800353fffff] on node 1
[  325.031775] [ffffea0001600000-ffffea00017fffff] potential offnode page_structs

Do you have plan to do it?

thanks for testing.

commit 5294828 from https://github.com/vliaskov/seabios/commits/memhp-v2
implements a SLIT table for the given numa nodes.

Hmm, why do you set node_distance(i, j) to REMOTE_DISTANCE if i != j?

However I am not sure the SLIT is the problem. The kernel builds a default
numa_distance table in arch/x86/mm/numa.c: numa_alloc_distance(). If the BIOS
doesn't present a SLIT, this should take effect (numactl --hardware should
report this table)

If the BIOS doesn't present a SLIT, numa_distance_cnt is set to 0 in the
function numa_reset_distance(). So node_distance(i, j) is REMOTE_DISTANCE(i != j).

Do you have more details on how to reproduce the warning? e.g. how many dimms
are present in the system? Does this happen on the first dimm hot-plugged?
Are all SRAT entries parsed correctly at boot-time or do you see any other
warnings at boot-time?

I can't reproduce it again. IIRC, I only do the following things:
hotplug a memory device, online the pages, offline the pages and hot remove
the memory device.

Thanks
Wen Congyang

I 'll investigate a bit more and report back.

thanks,

- Vasilis