Re: [Qemu-devel] [PATCH V9 06/12] NUMA: Add Linux libnuma detection

[Wanlong Gao]

On 08/26/2013 03:46 PM, Andrew Jones wrote:
>>> Is this patch still necessary? I thought that dropping the
>>> > > numa_num_configured_nodes() calls from patch 8/12 got rid
>>> > > of the need for this library. Maybe I missed other uses?
>> > 
>> > Yes, in 08/12 we also use mbind(), 
> You don't need a whole library for mbind(), it's a syscall. See syscall(2).
> 
>> > and in 09/12 we use max_numa_node().
> Really? I didn't see it there. And anyway, that goes back to our discussion
> about setting qemu's MAX_NODES to whatever we think qemu should support,
> and then just checking that we don't blow that limit whenever reading
> host node info, i.e.
> 
> maxnode = 0;
> while (host_nodes[maxnode] && maxnode < MAX_NODES)
>   node_read(&info[maxnode++]);
> 
> type of a thing.
> 
> And, if there's a place you really need to know the current online number
> of host nodes, then, like I said earlier, you should just go to sysfs
> yourself. libnuma:numa_max_node() returns an int that it only initializes
> at library load time, so it's not going to adapt to onlining/offlining.

OK, thank you.
Then I should define MPOL_* macros in QEMU and use mbind(2) syscall directly, 
right?

Thanks,
Wanlong Gao

> 
> drew
>