Date: Wed, 11 Mar 2015 09:55:56 +0100 From: Gary Jennejohn <gljennjohn@gmail.com> To: Alan Somers <asomers@freebsd.org> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, "lokadamus@gmx.de" <lokadamus@gmx.de>, "Pokala, Ravi" <rpokala@panasas.com>, Rui Paulo <rpaulo@me.com> Subject: Re: detecting hyperthreading Message-ID: <20150311095556.1ed29f5d@ernst.home> In-Reply-To: <CAOtMX2i6MOyHKc08GgyMgsxWcCWUUCTd2qHSnY=9WaZhUm2xdA@mail.gmail.com> References: <D12358C5.12F652%rpokala@panasas.com> <9F2E1411-B517-4BC8-AF61-BB15EE35083C@me.com> <D123957A.12F6CA%rpokala@panasas.com> <54FF1343.1020705@gmx.de> <D1246191.12F7D6%rpokala@panasas.com> <CAOjFWZ594OKAZ95ybegKiu%2BKr4-YeEZfJGVmv1obhxeZjVVbNA@mail.gmail.com> <CAOtMX2i6MOyHKc08GgyMgsxWcCWUUCTd2qHSnY=9WaZhUm2xdA@mail.gmail.com>
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On Tue, 10 Mar 2015 10:07:19 -0600 Alan Somers <asomers@freebsd.org> wrote: > On Tue, Mar 10, 2015 at 10:02 AM, Freddie Cash <fjwcash@gmail.com> wrote: > > On Tue, Mar 10, 2015 at 8:56 AM, Pokala, Ravi <rpokala@panasas.com> wrote: > > > >> -----Original Message----- > >> From: "lokadamus@gmx.de" <lokadamus@gmx.de> > >> Date: 2015-03-10, Tuesday at 08:52 > >> To: Ravi Pokala <rpokala@panasas.com>, Rui Paulo <rpaulo@me.com> > >> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> > >> Subject: Re: detecting hyperthreading > >> > >> >Have you look at dmesg? > >> >My system is a P4 with HTT. > >> >dmesg |more > >> [...] > >> >CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (3000.00-MHz 686-class CPU) > >> > Origin = "GenuineIntel" Id = 0xf29 Family = 0xf Model = 0x2 > >> >Stepping = 9 > >> > > >> >Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,M > >> >CA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE> > >> > Features2=0x4400<CNXT-ID,xTPR> > >> > >> Of course. :-) > >> > >> But there are two problems: > >> > >> (1) That just tells me HTT is supported by the CPU, not that if kernel is > >> using it. > >> (2) It's difficult to parse. > >> > >> Of the two, (1) is the bigger concern for my use-case. > >> > > > > 6 lines or so below the Features line shows the kernel loading "cpu0 > > (BSP)", and then "cpu1 (AP/HT)". > > > > Compare that to a system without HTT, where any extra cpus only show "(AP)". > > > > It's not perfect, but one could grep through /var/run/dmesg.boot looking > > for "cpu" lines and checking for "(AP)" or "(AP/HT)". > > > > -- > > Freddie Cash > > fjwcash@gmail.com > > I always look at "sysctl kern.sched.topology_spec" to tell if > hyperthreading is enabled. It's overkill, but it works. > [snip Ruby] Is this ULE-specific? This OID isn't present on my box using the BSD scheduler. Something to be aware of. -- Gary Jennejohn
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