December 20, 2005 at 2:25 am
I have seen various blogs stating that SQL Servers running on hyperthreading boxes can experience performance problems..
Is there a hotfix for this available or does anyone know if one is planned?
December 20, 2005 at 7:32 am
I haven't seen a hotfix announcement for this. It would probably take someone within Microsoft or privy to development within Microsoft to comment on whether or not one is planned. However, most hardware which supports hyperthreading give the option to disable hyperthreading in the BIOS.
K. Brian Kelley
@kbriankelley
December 21, 2005 at 9:06 am
Hyperthreading is not the same as adding a processor and doesn't work for every application.
The problem is a basic issue with hyperthreading and the software's design. These hyperthreads share L1 and L2 cache and can invalidate the other's cache more frequently than OS scheduled threads/processes, causing thrashing. Don't expect a "fix".
SQL Server is best run on multiple processors (with multiple caches) and without hyperthreading. At light loads you won't notice but at higher CPU loads you will.
December 21, 2005 at 9:42 am
This is true, and the support for hyperthreading differs between Windows 2000 and 2003, making a hotfix specifically for SQL Server that much more difficult. Windows 2000 will see the "hyperthreaded processors" but sees them basically the same as physical ones. Windows Server 2003 can tell the difference.
K. Brian Kelley
@kbriankelley
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