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RE: [PATCH v2 9/9] xen: introduce a Kconfig option to configure NUMA nodes number
- To: Julien Grall <julien@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- From: Wei Chen <Wei.Chen@xxxxxxx>
- Date: Mon, 18 Jul 2022 07:51:40 +0000
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- Cc: nd <nd@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 18 Jul 2022 07:51:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v2 9/9] xen: introduce a Kconfig option to configure NUMA nodes number
Hi Julien, Jan,
> -----Original Message-----
> From: Julien Grall <julien@xxxxxxx>
> Sent: 2022年7月14日 19:27
> To: Jan Beulich <jbeulich@xxxxxxxx>; Wei Chen <Wei.Chen@xxxxxxx>
> Cc: nd <nd@xxxxxxx>; Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; George
> Dunlap <george.dunlap@xxxxxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Roger Pau Monné
> <roger.pau@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 9/9] xen: introduce a Kconfig option to configure
> NUMA nodes number
>
> Hi Jan,
>
> On 14/07/2022 12:10, Jan Beulich wrote:
> > On 14.07.2022 12:14, Wei Chen wrote:
> >> Hi Jan,
> >>
> >>> -----Original Message-----
> >>> From: Jan Beulich <jbeulich@xxxxxxxx>
> >>> Sent: 2022年7月12日 22:34
> >>> To: Wei Chen <Wei.Chen@xxxxxxx>
> >>> Cc: nd <nd@xxxxxxx>; Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; George
> >>> Dunlap <george.dunlap@xxxxxxxxxx>; Julien Grall <julien@xxxxxxx>;
> Stefano
> >>> Stabellini <sstabellini@xxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Roger Pau
> Monné
> >>> <roger.pau@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> >>> Subject: Re: [PATCH v2 9/9] xen: introduce a Kconfig option to
> configure
> >>> NUMA nodes number
> >>>
> >>> On 08.07.2022 16:54, Wei Chen wrote:
> >>>> --- a/xen/arch/Kconfig
> >>>> +++ b/xen/arch/Kconfig
> >>>> @@ -17,3 +17,14 @@ config NR_CPUS
> >>>> For CPU cores which support Simultaneous Multi-Threading or
> >>> similar
> >>>> technologies, this the number of logical threads which Xen
> will
> >>>> support.
> >>>> +
> >>>> +config NR_NUMA_NODES
> >>>> + int "Maximum number of NUMA nodes supported"
> >>>> + range 1 255
> >>>> + default "64"
> >>>> + depends on NUMA
> >>>
> >>> Does 1 make sense? That's not going to be NUMA then, I would say.
> >>>
> >>
> >> Ok, we need at least 2 nodes to be a real NUMA.
> >>
> >>> Does the value being (perhaps far) larger than NR_CPUS make sense?
> >>>
> >>
> >> Arm has 128 default NR_CPUS (except some platforms) and x86 has 256.
> >> So I am not very clear about your comments about far larger? As my
> >> Understanding, one node has 2 or 4 cores are very common in a NUMA
> >> System.
> >
> > The defaults are fine. But does it make sense to have 255 nodes when
> > just 32 CPUs were selected? I'm afraid kconfig is going to get in the
> > way, but I think I'd like the upper bound to be min(NR_CPUS, 255).
>
> Looking around NUMA nodes with 0 CPUs exists. So I don't think we should
> tie the two.
>
Yes, some nodes can only have RAM and some nodes can only have CPUs.
So is it ok to use 2-255 for node range?
> Cheers,
>
> --
> Julien Grall
|
