4 ms·
I've never trusted hyperthreading for workloads I haven't tested. Sometimes it's faster, often it's slower. Beyond that, I've been suspicious of its security im
by Scramblejams 8y ago
I've never trusted hyperthreading for workloads I haven't tested. Sometimes it's faster, often it's slower. Beyond that, I've been suspicious of its security implications from day one. My first trip through the BIOS on a personal machine always includes turning it off.
- rythie 8y agoYou could just buy i5 based machines instead which don't have hyperthreading.
- deleted 8y ago[deleted]
- krylon 8y agoFrom what I have seen, I think many dual-core i5 CPUs for notebooks support hyperthreading.
- letsgetphysITal 8y agoThe U (ultra-low power) lines are indeed two-core with Hyperthreading. All others are 4 core without.
- krylon 8y agoOkay, that explains it. The only i5-based systems I have used (or still use) are notebooks.
- berbec 8y agoThis changed with 8th-gen Intel. The low-powers are now dual-HT/quad/quad-HT i3/i5/i7 [1]/[2]/[3] 1: https://ark.intel.com/products/137977/Intel-Core-i3-8130U-Processor-4M-Cache-up-to-3_40-GHz https://ark.intel.com/products/137977/Intel-Core-i3-8130U-Pr... 2: https://ark.intel.com/products/124969/Intel-Core-i5-8350U-Processor-6M-Cache-up-to-3_60-GHz https://ark.intel.com/products/124969/Intel-Core-i5-8350U-Pr... 3: https://ark.intel.com/products/122589/Intel-Core-i7-8550U-Processor-8M-Cache-up-to-4_00-GHz https://ark.intel.com/products/122589/Intel-Core-i7-8550U-Pr...
- rythie 8y agoYes, you're right, I was thinking only about desktop CPUs, forgetting the laptop CPUs are different.
- ailideex 8y agoCan you give example of where it was slower for you with HT enabled?
- Scramblejams 8y agoRunning finite element models with MSC NASTRAN, basically heavy matrix math. Matrices were NxN, N was around 10 million. This was on a server with 36 cores and a half terabyte of RAM, purchased in 2014. Also seen Erlang workloads where you could get a bit of throughput increase with your VM scheduler scheduling more threads than your physical cores (so starting to use HT) but the latency would spike and become very unpredictable, which was a bad tradeoff for the use case.
- gnufx 8y agoHPC workloads normally at least won't benefit and probably take a hit from HT on Xeon-ish hardware at least. It's normally turned off on HPC compute nodes (perhaps in software so the resource manager can enable per-job if necessary). There are exceptions, particularly with KNC and, perhaps, KNL. The situation is likely different for POWER, but I don't have experience of it.