Hello Recent Linux kernels (4.19 iirc) have a switch to toggle SMT in /sys/devices/system/cpu/smt/control (write "on" or "off" in this file). Current state can be read from /sys/devices/system/cpu/smt/active
Brice Le 22/10/2020 à 17:24, Alexander Kruppa via cfarm-users a écrit : > Hello, > > would it be possible to allow users to disable SMT (a.k.a. > hyperthreading) temporarily on one cpu core? This would be useful for > doing timing runs that are not affected by other processes running on > another logical cpu on the same physical core. > > This can be accomplished by taking all but one logical cpu on a > physical core offline via > /sys/devices/system/cpu/cpu*/online > For example, on gcc121, > $ head /sys/devices/system/cpu/cpu??/topology/thread_siblings_list | > tail -n 2 > ==> /sys/devices/system/cpu/cpu31/topology/thread_siblings_list <== > 15,31 > shows that logical cpus 15 and 31 are on the same physical core. With > # echo 0 > /sys/devices/system/cpu/cpu31/online > as root, logical cpu 31 can be taken offline, so that processes on > logical core 15 run effectively without SMT interference until logical > core 31 is put online again. > > Is there any interest in allowing such a mechanism? > > All the best, > Alex > > _______________________________________________ > cfarm-users mailing list > [email protected] > https://lists.tetaneutral.net/listinfo/cfarm-users
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