Comments on: Linux tips: How to find out if a your CPU supports HT (Hyper-Threading)? http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/ The Journal Of A Linux Sysadmin Tue, 07 Sep 2010 18:54:21 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: shawshankhttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-2/#comment-180584 shawshank Wed, 01 Jul 2009 09:33:32 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-180584 hi.. i understood that 'ht' in the /proc/cpuinfo flags section tells you that the cpu is capable of providing hyperthreading. But how can i find out if the kernel is enabled for hyperthreading. Is there a way by which I can programatically find out this? Please help.... hi.. i understood that ‘ht’ in the /proc/cpuinfo flags section tells you that the cpu is capable of providing hyperthreading.
But how can i find out if the kernel is enabled for hyperthreading. Is there a way by which I can programatically find out this?
Please help….

]]> By: fruitwerkshttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-2/#comment-180513 fruitwerks Tue, 23 Jun 2009 06:04:00 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-180513 The ht flag does not always mean that the CPU supports hyper-threading! If you are one linux and the kernel has SMP support and the BIOS is not disabling it, cat /proc/cpuinfo will show twice the processors than you actually have. if you have a single dual-core HT cpu, you will see 4 cores, the same for a dual cpu single core system with HT. This example is from a Dell PE2850 with two single-core xeons with HT;Found 4 CPUs -------------------------------------------------------------------------- CPU #1 EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3 CPU Model: Pentium 4 (Prescott) [N0] Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz Type: 0 (Original OEM) Brand: 0 (Unsupported) Number of cores per physical package=1 Number of logical processors per socket=2 Number of logical processors per core=2 APIC ID: 0x0 Package: 0 Core: 0 SMT ID 0 -------------------------------------------------------------------------- CPU #2 EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3 CPU Model: Pentium 4 (Prescott) [N0] Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz Type: 0 (Original OEM) Brand: 0 (Unsupported) Number of cores per physical package=1 Number of logical processors per socket=2 Number of logical processors per core=2 APIC ID: 0x6 Package: 1 Core: 0 SMT ID 0 -------------------------------------------------------------------------- CPU #3 EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3 CPU Model: Pentium 4 (Prescott) [N0] Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz Type: 0 (Original OEM) Brand: 0 (Unsupported) Number of cores per physical package=1 Number of logical processors per socket=2 Number of logical processors per core=2 APIC ID: 0x1 Package: 0 Core: 0 SMT ID 1 -------------------------------------------------------------------------- CPU #4 EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3 CPU Model: Pentium 4 (Prescott) [N0] Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz Type: 0 (Original OEM) Brand: 0 (Unsupported) Number of cores per physical package=1 Number of logical processors per socket=2 Number of logical processors per core=2 APIC ID: 0x7 Package: 1 Core: 0 SMT ID 1 --------------------------------------------------------------------------flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc pebs bts nopl pni monitor ds_cpl cid cx16 xtprI also have an old p4 with the ht flag, but it does not support HT! The ht flag does not always mean that the CPU supports hyper-threading! If you are one linux and the kernel has SMP support and the BIOS is not disabling it, cat /proc/cpuinfo will show twice the processors than you actually have. if you have a single dual-core HT cpu, you will see 4 cores, the same for a dual cpu single core system with HT. This example is from a Dell PE2850 with two single-core xeons with HT;

Found 4 CPUs
————————————————————————–
CPU #1
EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3
CPU Model: Pentium 4 (Prescott) [N0]
Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz
Type: 0 (Original OEM) Brand: 0 (Unsupported)
Number of cores per physical package=1
Number of logical processors per socket=2
Number of logical processors per core=2
APIC ID: 0×0 Package: 0 Core: 0 SMT ID 0
————————————————————————–
CPU #2
EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3
CPU Model: Pentium 4 (Prescott) [N0]
Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz
Type: 0 (Original OEM) Brand: 0 (Unsupported)
Number of cores per physical package=1
Number of logical processors per socket=2
Number of logical processors per core=2
APIC ID: 0×6 Package: 1 Core: 0 SMT ID 0
————————————————————————–
CPU #3
EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3
CPU Model: Pentium 4 (Prescott) [N0]
Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz
Type: 0 (Original OEM) Brand: 0 (Unsupported)
Number of cores per physical package=1
Number of logical processors per socket=2
Number of logical processors per core=2
APIC ID: 0×1 Package: 0 Core: 0 SMT ID 1
————————————————————————–
CPU #4
EFamily: 0 EModel: 0 Family: 15 Model: 4 Stepping: 3
CPU Model: Pentium 4 (Prescott) [N0]
Processor name string: Intel(R) Xeon(TM) CPU 3.00GHz
Type: 0 (Original OEM) Brand: 0 (Unsupported)
Number of cores per physical package=1
Number of logical processors per socket=2
Number of logical processors per core=2
APIC ID: 0×7 Package: 1 Core: 0 SMT ID 1
————————————————————————–

flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc pebs bts nopl pni monitor ds_cpl cid cx16 xtpr

I also have an old p4 with the ht flag, but it does not support HT!

]]> By: fruitwerkshttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-2/#comment-180346 fruitwerks Sun, 17 May 2009 18:52:11 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-180346 x86info can also tell you what is going on.Found 2 CPUs -------------------------------------------------------------------------- CPU #1 EFamily: 0 EModel: 0 Family: 15 Model: 1 Stepping: 2 CPU Model: Pentium 4 (Willamette) [D0] Processor name string: Intel(R) Xeon(TM) CPU 1.70GHz Type: 0 (Original OEM) Brand: 14 (Intel® Xeon processor) Number of cores per physical package=1 Number of logical processors per socket=1 Number of logical processors per core=1 APIC ID: 0x0 Package: 0 Core: 0 SMT ID 0 -------------------------------------------------------------------------- CPU #2 EFamily: 0 EModel: 0 Family: 15 Model: 1 Stepping: 2 CPU Model: Pentium 4 (Willamette) [D0] Processor name string: Intel(R) Xeon(TM) CPU 1.70GHz Type: 0 (Original OEM) Brand: 14 (Intel® Xeon processor) Number of cores per physical package=1 Number of logical processors per socket=1 Number of logical processors per core=1 APIC ID: 0x6 Package: 0 Core: 0 SMT ID 0 --------------------------------------------------------------------------but I do have HT!flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pebs bts x86info can also tell you what is going on.

Found 2 CPUs
————————————————————————–
CPU #1
EFamily: 0 EModel: 0 Family: 15 Model: 1 Stepping: 2
CPU Model: Pentium 4 (Willamette) [D0]
Processor name string: Intel(R) Xeon(TM) CPU 1.70GHz
Type: 0 (Original OEM) Brand: 14 (Intel® Xeon processor)
Number of cores per physical package=1
Number of logical processors per socket=1
Number of logical processors per core=1
APIC ID: 0×0 Package: 0 Core: 0 SMT ID 0
————————————————————————–
CPU #2
EFamily: 0 EModel: 0 Family: 15 Model: 1 Stepping: 2
CPU Model: Pentium 4 (Willamette) [D0]
Processor name string: Intel(R) Xeon(TM) CPU 1.70GHz
Type: 0 (Original OEM) Brand: 14 (Intel® Xeon processor)
Number of cores per physical package=1
Number of logical processors per socket=1
Number of logical processors per core=1
APIC ID: 0×6 Package: 0 Core: 0 SMT ID 0
————————————————————————–

but I do have HT!

flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pebs bts

]]> By: Llamahttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-2/#comment-180067 Llama Thu, 09 Apr 2009 22:03:50 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-180067 See /usr/src/linux/arch/x86/include/asm/cpufeature.h See /usr/src/linux/arch/x86/include/asm/cpufeature.h

]]> By: Mark Wilsonhttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-1/#comment-129802 Mark Wilson Wed, 20 Feb 2008 17:51:22 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-129802 Thanks for this Boris. Regards, Mark Thanks for this Boris. Regards, Mark

]]> By: Borishttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-1/#comment-129762 Boris Wed, 20 Feb 2008 15:03:12 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-129762 Hi Mark,check http://www.intel.com/design/xeon/applnots/241618.htm (pdf document, p. 24f) for all the flags explained.Regards, Boris. Hi Mark,

check http://www.intel.com/design/xeon/applnots/241618.htm (pdf document, p. 24f) for all the flags explained.

Regards,
Boris.

]]> By: - Marius -http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-1/#comment-87108 - Marius - Fri, 05 Oct 2007 21:49:58 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-87108 Hi Mark,Sorry I don't. Maybe you can find something like that on CPU manufacturers (intel or amd) developer sites. Hi Mark,

Sorry I don’t. Maybe you can find something like that on CPU manufacturers (intel or amd) developer sites.

]]> By: Mark Wilsonhttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-1/#comment-86784 Mark Wilson Thu, 04 Oct 2007 23:39:43 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-86784 Hi Marius, Do you have a complete list of what all the flags mean? CPU-Z for Windows and CPUID for Linux are useful tools, but it's all still a little bit cryptic!Mark Hi Marius,
Do you have a complete list of what all the flags mean? CPU-Z for Windows and CPUID for Linux are useful tools, but it’s all still a little bit cryptic!

Mark

]]> By: Naveenhttp://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-1/#comment-70799 Naveen Tue, 21 Aug 2007 09:03:54 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-70799 how can i check from the user interface if HT is enabled or not. my appication cant read the same from BIOS. how can i check from the user interface if HT is enabled or not.
my appication cant read the same from BIOS.

]]> By: - Marius -http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/comment-page-1/#comment-52069 - Marius - Tue, 19 Jun 2007 16:27:23 +0000 http://www.ducea.com/2006/06/23/linux-tips-how-to-find-out-if-a-your-cpu-supports-ht-hyper-threading/#comment-52069 Markus,this is most certainly caused by your kernel. Can you try to upgrade to the latest RHEL kernel and see if you see a difference? On stock kernels this info (core id) apparently appeared starting with 2.6.11: http://thread.gmane.org/gmane.linux.kernel/287715 The RHEL kernel is obviously not following the stock version with many 'internal' changes even if the version looks smaller. Anyway it should be a good idea to upgrade to the latest rhel kernel (if you are running rhel4 then this is probably kernel-smp-2.6.9-55.EL). Let me know... Markus,

this is most certainly caused by your kernel. Can you try to upgrade to the latest RHEL kernel and see if you see a difference? On stock kernels this info (core id) apparently appeared starting with 2.6.11:
http://thread.gmane.org/gmane.linux.kernel/287715
The RHEL kernel is obviously not following the stock version with many ‘internal’ changes even if the version looks smaller. Anyway it should be a good idea to upgrade to the latest rhel kernel (if you are running rhel4 then this is probably kernel-smp-2.6.9-55.EL).
Let me know…

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