on 07-24-2007 12:22 PM
Hi!
What about switching on hyperthreading on older CPUs?
There are very ambiguous "recommendations" one can hear...
Some say: If the processor can, switch it on.
Others say: SAP is not prepared for hyperthreading, so switch it off.
What may be the truth?
And what are the technical arguments?
What are your experiences?
Kind regards, Rudi
And: Don 't mix this up with dual core CPUs...
as told in
https://www.sap.com/documents/2016/09/2cbf0206-8a7c-0010-82c7-eda71af511fa.html
If you compare the SAME amount of physical cores, with the SAME amount of pysical cores + HT (= double amount of logical cores) then you can get a perdormance boost up to 10-30%.
Of course, if you compare e.g. 8 vCPUs to 8 pCPU, the vCPU setting will be much slower, as you only use the half amount of pCPU.
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Hi Rudolf,
SAP is a single threaded application. Each work process can affinitize to only one CPU, or more correctly OS thread.
With Hyperthreading 2 logical threads are presented to the OS for each physical core. Each of these threads has approximately half the SAPS of the physical CPU/core. Therefore long running CPU intensive batch jobs perform worse with hyperthreading.
There is no clear rule - you need to test your specific environment with your specific workload.
For SQL server the rule is simple. ALWAYS switch it off.
http://blogs.msdn.com/slavao/archive/2005/11/12/492119.aspx
Interesting to see what comments come up in this thread.
N.P.C
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