On 27/05/16 20:11, Alex Williamson wrote:
[re-adding vfio-users]
On Fri, 27 May 2016 15:03:17 -0400
chintu hetam <rometor...@gmail.com> wrote:
that worked Alex, sorry for the delay in response.
so my memorybacking configuration was
<memoryBacking>
<hugepages>
<page size='1048576' unit='KiB' nodeset='1'/>
</hugepages>
<nosharepages/>
<locked/>
</memoryBacking>
i had to remove it completely in order to make it work.
So confirming that hugepages and vfio has some issue, making VM to hang in
case of linux at startup and abruptly crashing from FreeBSD guest during
startup.
Can you see if the problem persists with updated QEMU from virt-preview:
https://fedoraproject.org/wiki/Virtualization_Preview_Repository
2MB hugepages certainly works, I run it daily. 1GB hugepages sees less
attention, but I certainly thought it worked as well. Thanks,
Alex
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I use both 2Mb and 1Gb pages in a pair of numa nodes and have never had
any problems with them except when memory has fragmented before I launch
the emulator. I've done this with qemu command line since about 2.4, but
I do remember 2Mb and 1Gb pages weren't supported on the same machine
until around kernel 2.4 ... or maybe they required a lot of work. Maybe
freebsd is like that.
Have you checked your hugepages directory? it needs to be writable to
the process running qemu and large enough to make the given files.
Libvirt may need something I don't know about especially if running as a
normal user.
I tend to have more than one mount point that has the fixed size I
require and the correct permissions / gid so the parameters are all in
one place and it's easy to test.
echo 3584 > "/sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages"
mount -t hugetlbfs -o
uid=0,gid=124,mode=0777,size=7168M,nr_inodes=3584,pagesize=2M hugetlbfs
$CDIR/qmp/hugepagesfs
There's a lot of ways to break hugepages in the kernel /proc/sys /sysfs
as well. I think if you don't use pre-alloc in qemu the pages can get
claimed and freed and fragmented / swapped out.
One last thought ... you don't need the balloon device if you've got a
fixed pre-allocated memory size as below
-m 32768 -mem-prealloc -mem-path /dev/hugepages/libvirt/qemu
doubt it matters ... although I also have trouble with some passthrough
devices if I don't use -cpu host with kvm and I have no idea why.
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