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

[Andrew Jones]

----- Original Message -----
> 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?

Hmm, yeah, that's too bad that numaif.h is part of libnuma, and not a more
general lib. Whether or not we want to redefine those symbols within
qemu, in order to avoid the dependency on installing numactl-devel, isn't
something I can answer. That's a better question for Anthony. Anthony? Paolo,
any opinions? Maybe we should pick up uapi/linux/mempolicy.h with the
linux-header synch script?

thanks,
drew

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