On Tue, Jun 09, 2015 at 05:52:04AM +0000, Vivi L wrote:
> Configure hugepages and then start virtual guest via "virsh start". However,
> virtual guest failed to use hugepages although it's configured
>
> The initial usage of system memory
> [root@local ~]# free
> total used free shared buff/cache available
> Mem: 263767352 1900628 261177892 9344 688832 261431872
> Swap: 4194300 0 4194300
>
> After configuring hugepages,
> [root@local ~]# cat /proc/meminfo | grep uge
> AnonHugePages: 2048 kB
> HugePages_Total: 140
> HugePages_Free: 140
> HugePages_Rsvd: 0
> HugePages_Surp: 0
> Hugepagesize: 1048576 kB
>
> [root@local ~]# mount | grep huge
> cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,
> relatime,hugetlb)hugetlbfs on /dev/hugepages type hugetlbfs (rw,realtime)
>
> On the guest side, its config xml contains
> <domain type='kvm'>
> <name>test-01</name>
> <uuid>e1b72349-4a0b-4b91-aedc-fd34e92251e4</uuid>
> <description>test-01</description>
> <memory unit='KiB'>134217728</memory>
> <currentMemory unit='KiB'>134217728</currentMemory>
> <memoryBacking>
> <hugepages/>
You might want re-test by explicitly setting the 'page' element and
'size' attribute? From my test, I had something like this:
$ virsh dumpxml f21-vm | grep hugepages -B3 -A2
<memory unit='KiB'>2000896</memory>
<currentMemory unit='KiB'>2000000</currentMemory>
<memoryBacking>
<hugepages>
<page size='2048' unit='KiB' nodeset='0'/>
</hugepages>
</memoryBacking>
<vcpu placement='static'>8</vcpu>
I haven't tested this exhaustively, but some basic test notes here:
https://kashyapc.fedorapeople.org/virt/test-hugepages-with-libvirt.txt
> <nosharepages/>
> </memoryBacking>
>
>
> Tried to virsh start the guest, but it failed although the hugepages memory
> was sufficient
> virsh # start test-01
> error: Failed to start domain test-01
> error: internal error: early end of file from monitor: possible problem:
> Cannot set up guest memory 'pc.ram': Cannot allocate memory
>
>
> however, if decrease the number of hugepages to smaller(say 100) that
> makes the memory not used by hugepages more than required by guest,
> then guest can start. But memory is not allocated from hugepages.
> [root@local ~]# cat /proc/meminfo | grep uge
> AnonHugePages: 134254592 kB
> HugePages_Total: 100
> HugePages_Free: 100
> HugePages_Rsvd: 0
> HugePages_Surp: 0
> Hugepagesize: 1048576 kB
>
> In summary, although hugepages is configured, the guest seemed not
> instructed to use hugepage, instead, the guest is allocated memory from
> the memory pool leftover by hugepages.
>
>
>
>
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/kashyap
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