Questions tagged [hyperthreading]

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Does a process filling all logical cores have a negative impact on performance? [closed]

Because of hyper-threading, my CPU has 2 logical processors per core. If I understand the premise of hyper-threading correctly, it allows each core to have a separate cache and instruction pointer for ...
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1answer
106 views

In Solaris box how do we check if hyper-threading/multi-threading is enabled or not using command?

In Solaris, how we can find the status or check hyper-threading or multi-threading is enabled or not using commands?
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1answer
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How hyperthreading is useful in kvm based guest VM?

We are creating virtual os threads inside guest os but the actual physical core is on the host machine. Will hyperthread = true in guest VM config make any difference? I can visualize how ...
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1answer
125 views

How to reliably tell from Linux whether the CPU supports Hyperthreading, even if Hyperthreading is disabled?

The following is what I am doing to tell whether a processor does support HT or not, regardless of whether it is enabled or disabled: # dmidecode -t processor | grep "Hardware Thread" | wc -l If ...
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1answer
90 views

Can hyperthread be enabled

I would like to know if hyperthread can be enabled on my operating system or not? I am using HP-UX Itanium, below is truncated output of machinfo Intel(R) Itanium(R) Processor 9560 (2.53 GHz, 32 ...
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1answer
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CMOS occasionally resets hyperthreading. Can I force hyperthreading on using Linux kernel?

I have some i7-4700EQ based embedded server systems that require hyperthreading. All is good except that, on rare occasions, the hyperthreading flag in CMOS gets set to disabled. While the hardware ...
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0answers
396 views

Hyper Threading and Process Priority

Are there any methods (linux kernel options, sysctl settings or configurable scheduler modules) that can cause a high priority process/thread to run on a physical processor core with the second (hyper ...
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0answers
1k views

How to tell if the CPU supports hyper threading

I know it should be a simple matter of grep -wl ht /proc/cpuinfo but that's not always accurate. I have an i5-7440HQ CPU which doesn't support hyper-threading (Intel, WikiPedia, and my BIOS agree on ...
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3answers
51k views

VirtualBox: Is it a bad idea to assign more virtual CPU cores than number of physical CPU cores

As I have a Hyper-Threading capable CPU, I wonder, is it a bad idea to assign more virtual CPU cores than number of physical CPU cores as the following warning suggests: Transcript: More virtual ...
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1answer
108 views

Are there UNIX variants or other OS which make user level threads visible to OS kernel? [closed]

Are there UNIX variants or other OS which make user level threads visible to OS kernel ?
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1answer
908 views

Processor affinity not respected by iperf threads

I'm running iperf in server mode on a Ubuntu box (14.04 LTS). The hardware is quad core with hyper-threading, so I have cores 0-7 available (0 is paired with 4, 1 with 5 and so on). I've set the ...
7
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1answer
12k views

What does “cpu MHz” field mean in the /proc/cpuinfo of a hyper-threading cpu?

The CPU is a i7-3770@3.40GHz. It has 4 cores and each core has 2 threads. Here is the dmidecode output: # dmidecode -t 4 # dmidecode 2.9 SMBIOS 2.7 present. Handle 0x0042, DMI type 4, 42 bytes ...
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0answers
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CPU load and hyperthreading [duplicate]

If I have two physical cores and hyperthreading enabled, is the CPU load computed against two cores or fours? In other words, is complete load indicated by 2.0 or 4.0?
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2answers
486 views

Plain installation vs Virtual machines - what is better for multicore? [closed]

We've currently bought a new server, with 64 GB of RAM and 8 cores with hyperthreading support. We are going to build a system using: nginx. apache. mysql. php So, the question is about performance: ...
4
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1answer
1k views

Unexpected processor/core counts for AMD processor

I wanted to determine if a machine has hyperthreading enabled or not. To determine this, I used advice I found online, which operates as follows: physical_proc_count = `grep "physical id" /proc/...
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1answer
3k views

Benefits of hyperthreading for an Oracle database

I'm running Oracle 10 on a blade450 g6. I have hyper-threading turned on but I have heard several people say that Oracle databases don't play well with it. Are there specific performance or ...
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2answers
3k views

Hyperthreading not detected by Linux [closed]

I have a Dell server with two Intel Xeon E5645 cpus, each cpu has 6 cores, and each core is hyperthreaded (i.e. should be equivalent to two virtual cores). I installed CentOS 6.2 on this server and it ...
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1answer
1k views

Hyperthread and processors Clock, Size, and Capacity

When I enable hyperthreading, CPU size and capacity decrease to about half the non-hyperthreaded value. Since most of my processes use only two cores, should I disable hyperthreading? lshw -C ...
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15answers
171k views

Checking if HyperThreading is enabled or not?

How can I check if hyperthreading is enabled on a Linux machine, using a perl script to check for it? I'm trying the following way: dmidecode -t processor | grep HTT Let me know if I'm on right ...
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1answer
4k views

Should I disable hyperthreading when concerned about performance of single-threaded applications?

I use a i5-2410M processor, which is setup to do hyperthreading by default on my laptop. Considering that this is a 2-core processor, this means it can do 4 threads at a time. This also means that ...
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2answers
3k views

How to find if hyperthreading is enabled on FreeBSD

Is it possible to find out if hyperthreading is enabled within the BSD kernel of a given machine without watching the boot up sequence?
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3answers
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How can I have 400% CPU occupied on 2 cores

I understand that Σ(%CPU) ≤ logicalcores*(1+ε) (where ε is measure and rounding error). But, how can I have on a 2 core system 2 different processes, each taking 200% of CPU (as measured by htop)? ...