Linked by Thom Holwerda on Fri 18th Nov 2005 20:04 UTC
Intel Intel's Hyperthreading Technology is being blamed for server performance problems. With both SQL Server and Citrix Terminal Server installations, HT-enabled motherboards show markedly degraded performance under heavy load. Disabling HT restores expected levels, according to reports from within the IT industry.
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RE[2]: HT -> obsolete
by voidlogic on Sat 19th Nov 2005 02:29 UTC in reply to "RE: HT -> obsolete"
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"Its in theory a great way to cover the performance hit from I/O requests which are just as slow as ever."

IO is interrupt driven so its not like the CPU is ever in a loop polling; however, you maybe right in the way that I could see HT perhaps help with interrupt handling. Do keep in mind that for a modern CPU I/O is really just a ram read becuase the data was put into memory via device directy via DMA.

Making memory on CPU like dies would be much much more expensive. If a die the size of a modern P4 has all cache I would guess it would about 3-4 MB. Think how much 256 MB of that would cost.

As to main memory latency, yeah its there, the number of wasted cycles varies for every CPU/BUS/RAM combination. Do keep in mind the whole reason caches, on board memory controllers and many modern CPU architectures exist is to make this latency less painful.

Edited 2005-11-19 02:35

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