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

[Andrew Jones]

----- Original Message -----
> On 08/23/2013 04:40 PM, Andrew Jones wrote:
> > 
> > 
> > ----- Original Message -----
> >> Add detection of libnuma (mostly contained in the numactl package)
> >> to the configure script. Can be enabled or disabled on the command line,
> >> default is use if available.
> >>
> >> Signed-off-by: Andre Przywara <address@hidden>
> >> Signed-off-by: Wanlong Gao <address@hidden>
> > 
> > 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.

drew

> 
> Thanks,
> Wanlong Gao
> 
> > 
> > drew
> > 
> 
> 
>