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Win2k and HT

[Hyperthreading and Windows…] For Windows NT and Windows 2000, the answer is “It doesn’t even know.” These operating systems are not hyperthreading-aware because they were written before hyperthreading was invented. If you enable hyperthreading, then each of your CPUs looks like two separate CPUs to these operating systems. (And will get charged as two separate CPUs for licensing purposes.) Since the scheduler doesn’t realize the connection between the virtual CPUs, it can end up doing a worse job than if you had never enabled hyperthreading to begin with.

— http://blogs.msdn.com/oldnewthing/archive/2004/09/13/228780.aspx

*d’oh*

This entry was posted by mika on Tuesday, September 14th, 2004 at 18:34 and is filed under Computer. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

2 Responses to “Win2k and HT”

  1. mp Says:
    September 16th, 2004 at 13:32

    So, does Linux really use the HT capabilities? Only if you tell it, doesn’t it? “make -j2” e.g.

  2. Michael Prokop Says:
    September 16th, 2004 at 13:59

    To speed up the software itself (as if there were two CPUs) you need HT-aware applications, otherwise the kernel does the scheduling on it’s own – AFAIK.

    Also see:
    http://kerneltrap.org/node/view/1783
    http://www-106.ibm.com/developerworks/linux/library/l-htl/