On Mon, March 25, 2013 1:39 pm, Jostein Chr. Andersen wrote: > On 03/25/2013 08:06 PM, david wrote: >> The laptop I'm considering (Zareason Verix 530) as replacement for my >> current one has a dual-core Intel i3 processor with hyperthreading. >> Zareason says there's no way to turn off HT in BIOS. >> >> I think folk on the list have said that HT causes problems with RT. So >> how can I disable hyperthreading? > > I can do like this in my Kubuntu system which have 8 kernels: > > sudo echo 0 > /sys/devices/system/node/node0/cpu0/online > sudo echo 0 > /sys/devices/system/node/node0/cpu2/online That should be all you need with two cores, turn off cpu 0 and 2, though most people turn off 1 and 3 :) > sudo echo 0 > /sys/devices/system/node/node0/cpu7/online Which is why the cpu 7 here. Linux sees the each core as two cpus, one for each thread. Not only might a thread be using too much time but there is also the overhead of context switching (invisible to the kernel) from one thread to the other. With hyper threading on, I can run jack at 64 frames with few xruns. With hyperthreading off, I can get down to 16 frames with guitarix running and no xruns. (10 year old single core p4 at 2.4G) Read up on some of the cnc projects where they require lower latency than audio. Lots of good info. Hyperthreading improves "performance" over all, but raises the latency audio can run at without dropouts. Once you hit 4 cores though, hyperthreading is more of a gimmick than a help. Every second thread/cpu can also be disabled on the kernel command line in grub: isolcpus= cpu_number[, cpu_number,...] The cnc people also use this to hide a cpu away from the OS so they can have full access to that cpu for just their application without the OS using it too. -- Len Ovens www.OvenWerks.net _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
