This issue is not new, but I hit it 3-4 times since last Sept. You can download CPU-Z from http://cpuid.com/. Run it and check the number you read from “Core Speed” is same as “Specification”. If not, you should modify server BIOS setting, making the server runs in full speed.
Posts Tagged ‘cpu configuration’
Does Your CPU Run in Full Speed?
2011/07/30Hyper Thread Or Not?
2011/06/08Last month I attended “the Microsoft SQL Server 2008 R2 Administration Training for SAP” hosted by our friend Cameron Gardiner in Hong Kong. During the session, Cameron showed us the benchmark results. (http://www.sap.com/solutions/benchmark/sd2tier.epx) I read the doc and noted the server configuration like “… 8 processors / 80 cores / 160 threads… ” Wait a second, 160 threads with 80 cores, HyperThread enabled?
In the old day we were told that HyperThread was not a good idea on SQL box. For more details you can read http://blogs.msdn.com/b/slavao/archive/2005/11/12/492119.aspx . More precise saying, it depends. But I saw HyperThread causing performance down before, around year 2009. I then discussed with Cameron if this the known best practice for SAP on SQL. The answer was yes, but the reason was for the new CPU architecture like Nehalem, Hyper-Threading is reintroduced along with an L3 Cache missing from most Core-based microprocessors. SAP was benefited by Hyper-Threading.
So my understandings:
1) Tradeoff of HyperThread is the shared processor cache may be emptied by one thread.
2) Processor cache is not so important as the old day due to the new CPU technology.
3) We can enjoy the benefit of HyperThread more safely.
Of cause it depends, you should test how your application performing in your own box.
HTH.