Hyperthreading performance problems

It seems that Intel’s hyperthreading chip technology, rather than actually improving performance, could be having the opposite effect, according to an interesting article by Rupert Goodwins at ZDNet.

Hyper-threading, officially called Hyper-Threading Technology (HTT), is intended to speed performance by allowing a single processor to function like two separate processors by simultaneously running different code in separate parts of the processor.

But according to Goodwin’s article there are reports within the industry that HT-enabled motherboards, when under heavy load, are showing much worse levels of performance than would be expected. Disabling hyperthreading appears to return performance back to normal.

A recent post on an official Microsoft blog by developer Slava Ocks reinforces these claims. According to Ocks, some SQL customers noticed that, “when high load is applied SQL Server CPU usage increases significantly but SQL Server performance degrades.” Again, disabling hyperthreading returned performance to appropriate levels.

It seems the problem arises when, under certain circumstances, the chip’s shared memory cache can’t keep pace with the multiple threads being processed by the hyperthreading technology. Ocks blog has a more detailed analysis here.

It has been a tough time for Intel recently so it will be interesting to hear the chip giant’s response to these latest observations.