Date: Wed, 4 Jan 2017 18:06:16 +1030 From: Shane Ambler <FreeBSD@ShaneWare.Biz> To: Eric Joyner <erj@freebsd.org>, freebsd-questions <freebsd-questions@freebsd.org> Subject: Re: How many CPU cores does FreeBSD support? Message-ID: <fe302411-d085-cc53-b2bb-4670a9c302fe@ShaneWare.Biz> In-Reply-To: <CA%2Bb0zg-RYZgK67PsUAiSTss6WK2%2BFg_L4=zya33OxaiH%2BOfQHQ@mail.gmail.com> References: <CA%2Bb0zg-RYZgK67PsUAiSTss6WK2%2BFg_L4=zya33OxaiH%2BOfQHQ@mail.gmail.com>
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On 04/01/2017 08:08, Eric Joyner wrote: > I have an 11.0-RELEASE-p1 system with: > > hw.model: Intel(R) Xeon Phi(TM) CPU 7250 @ 1.40GHz > > It's got 68 cores, but with 4-way SMT, I think it should show up with 272 > logical cores on FreeBSD. > > However, in both kern.sched.topology_spec and hw.ncpu, it shows there are > only 223 cores. > > Is the limit effectively 223 cores, even though I see some #define MAXCPU > 256 lines in the source? You will probably find freebsd-current a better mailing list for this. How many show in dmesg? From https://svnweb.freebsd.org/base?view=revision&revision=270223 Bump MAXCPU on amd64 from 64 to 256. In practice APIC only permits 255 CPUs (IDs 0 through 254). Getting above that limit requires x2APIC. Also note that changing MAXCPU breaks ABI compatability so you will need to recompile. https://svnweb.freebsd.org/base?view=revision&revision=284720 -- FreeBSD - the place to B...Software Developing Shane Ambler
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