Date: Tue, 10 Mar 2015 10:19:21 +0900 From: Rui Paulo <rpaulo@me.com> To: "Pokala, Ravi" <rpokala@panasas.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: detecting hyperthreading Message-ID: <9F2E1411-B517-4BC8-AF61-BB15EE35083C@me.com> In-Reply-To: <D12358C5.12F652%rpokala@panasas.com> References: <D12358C5.12F652%rpokala@panasas.com>
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On 10 Mar 2015, at 06:03, Pokala, Ravi <rpokala@panasas.com> wrote: >=20 > Hi folks, >=20 > There used to be a sysctl, "machdep.hyperthreading_allowed", which > indicated whether or not the kernel was using hyperthreaded cores. It > looks like it was removed sometime between 8 and 9, for perfectly good > reasons = (https://svnweb.freebsd.org/base?view=3Drevision&revision=3D222853). >=20 > That said, is there currently a way to tell at runtime from userland = if > hyperthreading is enabled or not? I think that sysctl didn't fully control hyperthreading: you can disable = it on the BIOS and FreeBSD never exported that information. If you used = that tunable, it would simply disable the Pentium 4 Hyperthreading. -- Rui Paulo
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