Re: [Xen-devel] Question about memory allocation on NUMA node.

Andre Przywara
Fri, 17 Oct 2008 12:10:49 -0000

Yuji,

> I have a question about memory allocation on NUMA node for Xen
> Hypervisor.
>
> I think that the memory relating guest domain should be allocated from
> the NUMA node on which the guest run.
> Because the latency of the same NUMA node is better than that of a
> different one.
>
> According to this idea, most of the codes are good in xen-unstable.
> But some memory relating guest domain are allocated from the NUMA node
> on which CPU #0 run.
No, it will default to the node on which the domain runs, see
below.
>
> For example,
>     - xen/arch/x86/domain.c
>         setup_compat_l4(struct vcpu *v)
>           struct page_info *pg = alloc_domheap_page(NULL, 0);
0 for memflags means default behaviour, if you look at the
implementation of alloc_domheap_pages
(http://lxr.xensource.com/lxr/source/xen/common/page_alloc.c?a=x86_64#L774)
a value of zero will evalutate to node=NUMA_NO_NODE, which in turn
will be replaced by ''node = domain_to_node(d);'', which is what
you
wanted to insert below. So I see no problem here.

Regards,
Andre.

>
> I think this memory should be allocated from the NUMA node on which
> the guest run.
>
> For example,
>     - xen/arch/x86/domain.c at
>         setup_compat_l4(struct vcpu *v)
>           struct page_info *pg = alloc_domheap_page(NULL,
>                                  MEMF_node(domain_to_node(v->domain)));
>
> As a result, machine performance becomes better.
>
> What do you think about this idea?
> I''d like some comments.
>
> If the developers agree with me, I would like to list them and submit
> patch.
>
--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 277-84917
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