On Mon, May 20, 2013 at 10:03:53AM +0800, Wanlong Gao wrote:
>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
>
Hi Wanlong,
>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?
>
AutoNUMA is not merged currently, the foundation(automatic NUMA
balancing) that either the policy for schednuma or autonuma can be
rebased on implemented by Mel has already merged.
Regards,
Wanpeng Li
>
>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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