Re: [Qemu-devel] [RFC PATCH v0] numa: API to lookup NUMA node by address

[Igor Mammedov]

On Mon, 8 Jun 2015 11:28:18 +0530
Bharata B Rao <address@hidden> wrote:

> On Mon, May 25, 2015 at 02:42:40PM -0300, Eduardo Habkost wrote:
> > On Mon, May 25, 2015 at 01:17:57PM +0530, Bharata B Rao wrote:
> > > On Thu, May 14, 2015 at 11:39:06AM +0200, Paolo Bonzini wrote:
> > > > On 13/05/2015 20:06, Eduardo Habkost wrote:
> > > > > Also, this introduces a circular dependency between pc-dimm.c and
> > > > > numa.c. Instead of that, pc-dimm could simply notify us when a new
> > > > > device is realized (with just (addr, end, node) as arguments), so we 
> > > > > can
> > > > > save the list of memory ranges inside struct node_info.
> > > > > 
> > > > > I wonder if the memory API already provides something that would help
> > > > > us. Paolo, do you see a way we could simply use a MemoryRegion as 
> > > > > input
> > > > > to lookup the NUMA node?
> > > > 
> > > > No, but I guess you could add a numa_get/set_memory_region_node_id API
> > > > that uses a hash table.  That's a variant of the "pc-dimm could simply
> > > > notify" numa.c that you propose above.
> > > 
> > > While you say we can't use MemoryRegion as input to lookup the NUMA node,
> > > you suggest that we add numa_get/set_memory_region_node_id. Does this API
> > > get/set NUMA node id for the given MemoryRegion ? 
> > 
> > I was going to suggest that, but it would require changing the
> > non-memdev code path to create a MemoryRegion for each node, too. So
> > having a numa_set_mem_node_id(start_addr, end_addr, node_id) API would
> > be simpler.
> 
> In order to save the list of memory ranges inside node_info, I tried this
> approach where I call
> 
> numa_set_mem_node_id(dimm.addr, dimm.size, dimm.node) from
> 
> pc_dimm_realize(), but
> 
> the value of dimm.addr is finalized only later in ->plug().
> 
> So we would have to call this API from arch code like pc_dimm_plug().
> Is that acceptable ?
Could you query pc_dimms' numa property each time you need mapping
instead of additionally storing that mapping elsewhere?

> 
> Regards,
> Bharata.
> 
>