Messages in this thread | | | Subject | Re: [PATCH] arm64: NUMA: Kconfig: Increase max number of nodes | From | Robin Murphy <> | Date | Thu, 22 Oct 2020 00:44:15 +0100 |
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On 2020-10-21 12:02, Jonathan Cameron wrote: > On Wed, 21 Oct 2020 09:43:21 +0530 > Anshuman Khandual <anshuman.khandual@arm.com> wrote: > >> On 10/20/2020 11:39 PM, Valentin Schneider wrote: >>> >>> Hi, >>> >>> Nit on the subject: this only increases the default, the max is still 2¹⁰. >> >> Agreed. >> >>> >>> On 20/10/20 18:34, Vanshidhar Konda wrote: >>>> The current arm64 max NUMA nodes default to 4. Today's arm64 systems can >>>> reach or exceed 16. Increase the number to 64 (matching x86_64). >>>> >>>> Signed-off-by: Vanshidhar Konda <vanshikonda@os.amperecomputing.com> >>>> --- >>>> arch/arm64/Kconfig | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >>>> index 893130ce1626..3e69d3c981be 100644 >>>> --- a/arch/arm64/Kconfig >>>> +++ b/arch/arm64/Kconfig >>>> @@ -980,7 +980,7 @@ config NUMA >>>> config NODES_SHIFT >>>> int "Maximum NUMA Nodes (as a power of 2)" >>>> range 1 10 >>>> - default "2" >>>> + default "6" >>> >>> This leads to more statically allocated memory for things like node to CPU >>> maps (see uses of MAX_NUMNODES), but that shouldn't be too much of an >>> issue. >> >> The smaller systems should not be required to waste those memory in >> a default case, unless there is a real and available larger system >> with those increased nodes. >> >>> >>> AIUI this also directly correlates to how many more page->flags bits are >>> required: are we sure the max 10 works on any aarch64 platform? I'm >> >> We will have to test that. Besides 256 (2 ^ 8) is the first threshold >> to be crossed here. >> >>> genuinely asking here, given that I'm mostly a stranger to the mm >>> world. The default should be something we're somewhat confident works >>> everywhere. >> >> Agreed. Do we really need to match X86 right now ? Do we really have >> systems that has 64 nodes ? We should not increase the default node >> value and then try to solve some new problems, when there might not >> be any system which could even use that. I would suggest increase >> NODES_SHIFT value upto as required by a real and available system. > > I'm not going to give precise numbers on near future systems but it is public > that we ship 8 NUMA node ARM64 systems today. Things will get more > interesting as CXL and CCIX enter the market on ARM systems, > given chances are every CXL device will look like another NUMA > node (CXL spec says they should be presented as such) and you > may be able to rack up lots of them. > > So I'd argue minimum that makes sense today is 16 nodes, but looking forward > even a little and 64 is not a great stretch. > I'd make the jump to 64 so we can forget about this again for a year or two. > People will want to run today's distros on these new machines and we'd > rather not have to go around all the distros asking them to carry a patch > increasing this count (I assume they are already carrying such a patch > due to those 8 node systems)
Nit: I doubt any sane distro is going to carry a patch to adjust the *default* value of a Kconfig option. They might tune the actual value in their config, but, well, isn't that the whole point of configs? ;)
Robin.
> > Jonathan > >> >>> >>>> depends on NEED_MULTIPLE_NODES >>>> help >>>> Specify the maximum number of NUMA Nodes available on the target >>> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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