Date: Wed, 11 Mar 2015 09:19:56 -0600 From: Alan Somers <asomers@freebsd.org> To: gljennjohn@gmail.com 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: <CAOtMX2g%2BeZv=duELT3an2Q6wdTaM1mrq7iWtpVW1RO6i8vof5w@mail.gmail.com> In-Reply-To: <20150311095556.1ed29f5d@ernst.home> 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> <20150311095556.1ed29f5d@ernst.home>
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On Wed, Mar 11, 2015 at 2:55 AM, Gary Jennejohn <gljennjohn@gmail.com> wrote: > 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 I never noticed because I don't use the BSD scheduler. But now that you mention it, yes it is. The OID is defined in kern/sched_ule.c.
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