Sunday, June 26, 2011

Best way to check Hyper-threading feature in Linux

Run "dmidecode -t processor" and grep for the entry "HTT" from the result.

Sample output:

[root@server10 ~]# dmidecode -t processor | grep HTT
HTT (Hyper-threading technology)
HTT (Hyper-threading technology)
[root@server10 ~]#

So if Hyper-threading is enabled, the count of Logical Processors would be double the number of CPU cores that you got on the server.
To find the number of CPU cores, you either use "dmidecode -t processor" command or check the number of Physical IDs from "/proc/cpuinfo" output.

Please be aware the “ht” entry in /proc/cpuinfo output is a confusing flag. It may be definite for CPU with single core but not for multi-core CPU. Enabling HT should be done at BIOS level.

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