Adding CC AutoNUMA folks:
Paolo said that:
> Pinning memory to host NUMA nodes is not implemented. Something like
> AutoNUMA would be able to balance the memory the right way.
>
> Paolo
And Eduardo said that:
> I had plans to implement a mechanism to allow external tools to
> implement manual pinning, but it is not one of my top priorities. It's
> the kind of mechanism that may be obsolete since birth, if we have
> AutoNUMA working and doing the right thing.
>
> -- Eduardo
But I didn't see any change when I enabled the AutoNUMA on my host.
Can AutoNUMA folks teach me why?
Or any plans to handle this problem in AutoNUMA?
Thanks,
Wanlong Gao
> Hi,
>
> We just met a problem of QEMU memory allocation.
> Here is the description:
>
> On my host, I have two nodes,
> # numactl -H
> available: 2 nodes (0-1)
> node 0 cpus: 0 2
> node 0 size: 4010 MB
> node 0 free: 3021 MB
> node 1 cpus: 1 3
> node 1 size: 4030 MB
> node 1 free: 2881 MB
> node distances:
> node 0 1
> 0: 10 20
> 1: 20 10
>
>
>
> I created a guest using the following XML:
>
> ...
> <memory unit='KiB'>1048576</memory>
> <currentMemory unit='KiB'>1048576</currentMemory>
> <vcpu placement='static'>2</vcpu>
> <cputune>
> <vcpupin vcpu='0' cpuset='2'/>
> <vcpupin vcpu='1' cpuset='3'/>
> </cputune>
> <numatune>
> <memory mode='strict' nodeset='0-1'/>
> </numatune>
> <cpu>
> <topology sockets='2' cores='1' threads='1'/>
> <numa>
> <cell cpus='0' memory='524288'/>
> <cell cpus='1' memory='524288'/>
> </numa>
> </cpu>
> ...
>
> As you can see, I assigned 1G memory to this guest, pined vcpu0 to the host CPU 2,
> it's in host node0, pined vcpu1 to the host CPU 3 that is in host node1.
> The guest also has two nodes, each node contains 512M memory.
>
> Now, I started the guest, then printed the host numa state :
> # numactl -H
> available: 2 nodes (0-1)
> node 0 cpus: 0 2
> node 0 size: 4010 MB
> node 0 free: 2647 MB <=== freecell of node0
> node 1 cpus: 1 3
> node 1 size: 4030 MB
> node 1 free: 2746 MB
> node distances:
> node 0 1
> 0: 10 20
> 1: 20 10
>
> Then I tried to allocate memory from guest node0 using the following code:
>> #include <memory.h>
>> #include <numa.h>
>>
>> #define MEM (1024*1024*300)
>>
>> int main(void)
>> {
>> char *p = numa_alloc_onnode(MEM, 0);
>> memset(p, 0, MEM);
>> sleep(1000);
>> numa_free(p, MEM);
>> return 0;
>> }
>
> And printed the host numa state, it shows that this 300M memory is allocated from host node0,
>
> # numactl -H
> available: 2 nodes (0-1)
> node 0 cpus: 0 2
> node 0 size: 4010 MB
> node 0 free: 2345 MB <===== reduced ~300M
> node 1 cpus: 1 3
> node 1 size: 4030 MB
> node 1 free: 2767 MB
> node distances:
> node 0 1
> 0: 10 20
> 1: 20 10
>
>
> Then, I tried the same method to allocate 300M memory from guest node1, and printed the host
> numa state:
>
> # numactl -H
> available: 2 nodes (0-1)
> node 0 cpus: 0 2
> node 0 size: 4010 MB
> node 0 free: 2059 MB <=== reduced ~300M
> node 1 cpus: 1 3
> node 1 size: 4030 MB
> node 1 free: 2767 MB <=== no change
> node distances:
> node 0 1
> 0: 10 20
> 1: 20 10
>
>
> To see that this 300M memory is allocated from host node0 again, but not host node1 as
> I expected.
>
> We think that QEMU can't handled this numa memory allocation well, and it will cause the
> cross node memory access performance regression.
>
> Any thoughts? Or, am I missing something?
>
>
> Thanks,
> Wanlong Gao
>
>
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