Hi Julien, Jan, > -----Original Message----- > From: Julien Grall <jul...@xen.org> > Sent: 2022年7月14日 19:27 > To: Jan Beulich <jbeul...@suse.com>; Wei Chen <wei.c...@arm.com> > Cc: nd <n...@arm.com>; Andrew Cooper <andrew.coop...@citrix.com>; George > Dunlap <george.dun...@citrix.com>; Stefano Stabellini > <sstabell...@kernel.org>; Wei Liu <w...@xen.org>; Roger Pau Monné > <roger....@citrix.com>; xen-devel@lists.xenproject.org > 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 <jbeul...@suse.com> > >>> Sent: 2022年7月12日 22:34 > >>> To: Wei Chen <wei.c...@arm.com> > >>> Cc: nd <n...@arm.com>; Andrew Cooper <andrew.coop...@citrix.com>; George > >>> Dunlap <george.dun...@citrix.com>; Julien Grall <jul...@xen.org>; > Stefano > >>> Stabellini <sstabell...@kernel.org>; Wei Liu <w...@xen.org>; Roger Pau > Monné > >>> <roger....@citrix.com>; xen-devel@lists.xenproject.org > >>> 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
