[email protected] said: > I'm currently deciding between the Xeon E3-1220 (no Hyper-Threading) and > E3-1230 (Hyper-Threading). What's the consensus on HT on Illumos/KVM - could > I get a significant performance gain from turning on HT, or is it better to > leave it off? The VMs are not going to be running any intensive > multithreaded applications.
It's unlikely you'll know if HT is of benefit until you try it. One trick I've found to be helpful, especially on my older P4 CPU's with hyperthreading, is to use "psradm -i" to put half of the virtual CPU's into no-interrupt mode. The idea is to allow only one thread per CPU core to handle interrupts, leaving the other threads to be used for other computation. This strategy was recommended by Sun for the older "CoolThreads" UltraSPARC T1 CPU's, which had 8 threads per core. These cores were relatively slow, as compared to conventional processors, and the strategy of allowing only one thread per core to handle interrupts evidently cut down on the overhead of context-switching, cache-coherency, etc., and also made it easier to avoid overloading any single core. As I said, it seemed to improve overall throughput and interactive responsiveness on my older hyperthreaded machines. Can't tell any difference when applying it to my Core i7 desktop machine, though. Regards, Marion ------------------------------------------- illumos-discuss Archives: https://www.listbox.com/member/archive/182180/=now RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175430-2e6923be Modify Your Subscription: https://www.listbox.com/member/?member_id=21175430&id_secret=21175430-6a77cda4 Powered by Listbox: http://www.listbox.com
