Here's where I may put my foot in my mouth. If I'm not mistaken programs have to be compiled with a hyperthreading library in order to take advantage of this. Or am I wrong? On Sep 7, 2016 1:27 PM, "Kevin Fries" wrote: > I once worked for a company doing ground water modeling for mining > operations. The program did a large series of fourier transformation to > model the water levels over time... No Hyperthreading!!! > > Most web servers, mail servers, database servers (depending on your number > of indexes), are perfectly fine with hyperthreading turned on. > > Kevin > > On Sep 7, 2016 2:21 PM, "Carruth, Rusty" wrote: > >> Kevin, >> >> >> >> Do you have a reference to the ‘heavy use by one process on a cpu core >> can affect any other process’? (BTW, Affect, not Effect in this case. >> This is only going to you, regardless of what it looks like, so this is >> just between me an you unless you reply all, in which case it goes global, >> as it were) >> >> >> >> In any case, what little experimenting I did a while back indicated that, >> when Intel hyperthreads, what happens is effectively half of the cpu runs >> one thread, and the other half runs the other thread. >> >> >> >> So, for windows, where it does a TERRIBLE job (or it used to) of >> pre-emptive multitasking, having ‘more’ CPUs is better so that the OS can >> lock one down because it doesn’t know how to share it - thus hiding the bug. >> >> >> >> In linux, IMHO you should turn multithreading off. >> >> >> >> (IIRC, I ran a system with HT on, and looked at BogoMIPS, then ran with >> HT off, and the BogoMIPS doubled. I could be remembering wrong, and it was >> in the early days of HT, so perhaps they’ve “fixed” it) >> >> >> >> Rusty >> >> >> >> *From:* plug-discuss-bounces@lists.phxlinux.org [mailto: >> plug-discuss-bounces@lists.phxlinux.org] *On Behalf Of *Kevin Fries >> *Sent:* Wednesday, September 07, 2016 12:51 PM >> *To:* Main PLUG discussion list >> *Subject:* Re: 4 cores and 8 threads >> >> >> >> The big thing to keep in mind is this.... >> >> All threading either at the processor or in code will share a resource. >> Heavy use by one process on a CPU core can effect any other process running >> on that core. Heavy use on one CPU core will not effect the other cores. >> (sorta, as data bus issues can still occur). >> >> Most processes use very little actual CPU. So, between the OS and the >> multicores, modern computers can push allot of work through themselves. >> >> That said, there are some processes that are highly comparative. >> Multicores can actually slow down execution in these cases because any type >> of multiuse of a resource will encounter administrative overhead. But >> these processes are the exception, not the rule. If you have such needs, >> turn Hyperthreading off. Generally leave it on, and the the hardware do >> its job. >> >> Kevin >> >> >> >> On Sep 7, 2016 1:36 PM, "Jerry Snitselaar" wrote: >> >> On Tue Sep 06 16, Keith Smith wrote: >> >> >> >> Hi, >> >> If an Intel CPU has 4 cores and 8 threads will it look like 8 cores to >> VirtualBox when assigning resources to a guest? >> >> If so is there a way to determine which is a tread and which is actually >> a core? >> >> Thanks!! >> Keith >> --------------------------------------------------- >> PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org >> To subscribe, unsubscribe, or to change your mail settings: >> http://lists.phxlinux.org/mailman/listinfo/plug-discuss >> >> >> In addition to the answers already given, you can read >> about it in Volume 1 of the Intel Software Developer's Manual, >> section 2.2.8. >> >> http://www.intel.com/content/www/us/en/processors/architectu >> res-software-developer-manuals.html >> >> As to your question, if you have a hyperthreaded CPU it will look like >> multiple cores and there is no difference between them as far as >> you're concerned. >> --------------------------------------------------- >> PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org >> To subscribe, unsubscribe, or to change your mail settings: >> http://lists.phxlinux.org/mailman/listinfo/plug-discuss >> > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss >