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Questions tagged [hyperthreading]

In a hyperthreaded CPU, for each processor core that is physically present, the operating system addresses two virtual or logical cores, and shares the workload between them when possible.

In an hyper threaded environment, For each processor core that is physically present, the operating system addresses two virtual or logical cores, and shares the workload between them when possible.

This allows to decrease the number of dependent instructions on the pipeline. It takes advantage of superscalar architecture (multiple instructions operating on separate data in parallel).

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Sharing a TLB entry between two logical CPUs (Intel)

I wondered if it is possible if two threads belonging to the same program with the same PCID can share the TLB entry when they are scheduled to run on the same physical CPU? I already looked into the SDM…
Benedict Schlüter
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How to bind a process to only physical cores in a cross system way?

I’m using a project where each time you double the number of threads, you add between 40% to 60% overhead. As hyperthreading increases performance to a maximum of 30% this means, the program runs slower than in single thread mode on hyperthreaded…
user2284570
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Can a hyper-threaded processor core execute two threads at the exact same time?

I'm having a hard time understanding hyper-threading. If the logical core doesn't actually exist, what's the point of using hyper-threading?. The wikipedia article states that: For each processor core that is physically present, the operating…
Trey
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How to determine the optimal number of java threads when using a hyperthreaded multi core CPU

My CPU is 8x2600 MHz (Intel Xeon CPU E5-2670 0 @ 2.60GHz). I have a data processing algorithm which can run in parallel written in Java. This function determines the number of concurrent threads during runtime with…
Priyan Chandrapala
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Hyperthreading and thread priorities

Is there any way, other than to disable half of the cores using SetThreadAffinityMask(), to make a hyper-threading CPU fully obey thread priorities? AFAIK, the CPU itself is not aware of priorities, so a low priority thread running on core 1 will…
Sven Nilsson
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Apache Spark - virtual or physical cores used?

I have a Apache Spark 1.6.1 standalone cluster set on a single machine with the following specifications: CPU: Core i7-4790 (# of cores: 4, # of threads: 8) RAM: 16GB If I have the following configuration: SPARK_WORKER_INSTANCES =…
User2130
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use all cores of CPU

I want to use parallel computing on matlab, i have i7-960 CPU with 4 cores and 8 threads, when i run feature('numCores') command in matlab, i obtain this feature('numCores') MATLAB detected: 3 physical cores. MATLAB detected: 6 logical…
ensberg
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Relation between CPU's hyperthreading and OS's context switch?

Hyperthreading of a cpu core means the core can be treated as logically two or more logical/virtual cpu cores to run multiple processes. An operating system also provides concurrency programming, by scheduling and context switch. Do the two do the…
Tim
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How to set the maximum simultaneous requests that can be handled by a servlet using Tomcat

I wanted to know how many simultaneous requests a web application built using a servlet can handle (using Tomcat 7). I have configured maxThreads, acceptCount, minSpareThreads attributes of server.xml file. My question is: Do we have to take the…
Chris
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x86 Hyper-threading clarification on cache miss

If I understood correctly on x86 cpu hyper threading is beneficial especially when we have IO calls so that when blocking thread is idle another thread can cheaply work on the same CPU. My question is if the same thing happens on a cache miss as…
Onur Gumus
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Disable and Enable Hyperthreads on-the-fly

I am wondering if it is, in theory, possible to enable hyperthreads after they have been disabled in the BIOS and vice-versa. As it turns out, if hyper-threads are disabled they do still show up in the MADT tables of ACPI as disabled cores. This is…
zgerd
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how many instructions can it execute in one second?

A processor has 4 cores Each core has 2 - Hyper threads Its clock frequency is 2 GHz On average, an instruction needs 4 cpu cycles to execute on each hyperthread How many instructions can it execute in one second? I need help as to which…
user1988365
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Hyper-threading Performance Comparison

I have written a project, which uses some basic functions in openssl such as RAND_bytes and des_ecb_encrypt. My computer has i7-2600(4 cores and 8 logic CPU). When I run my project with 4 threads, it will costs 10 seconds. When I run it with 8…
Yulong Tian
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MPI Hostfiles with Hyperthreading

I'm running some small MPI jobs across nodes in a computer lab at my university. There's no queuing system installed, so I have to generate MPI hostfiles myself each time I want to run a job, then run them like so: mpirun --hostfile mpi_hostfile -n…
xiii1408
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Determining the independent CPU's (specified with affinity ID's) for building ATLAS

I'm trying to determine the independent CPU's (specified with affinity ID's) for building ATLAS on a linux machine with 4 Intel CPU's with hyperthreading (ubuntu 12.04). The reason I'm doing this is that the ATLAS manual says to use only the…
boojum
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