-----Original Message----- From: centos-bounces@xxxxxxxxxx [mailto:centos-bounces@xxxxxxxxxx] On Behalf Of Peter Kjellström Sent: den 9 mars 2012 11:05 To: centos@xxxxxxxxxx Subject: Re: HT (Hyper Threading) on CentOS 5.5 > I know there might be some negative performance issues with certain > applications, but would you notice it in day-to-day use? Negative performance due to HT comes in several flavours. Some compute intensive loads simply perform a bit better with HT off (usually measureable but not really noticeable, 1-10% is expected here). Another way HT can cause you performance degradation is due to incorrect scheduling and/or pinning. What happens then is that two threads are (incorrectly) put on the same core instead of using two cores (impact: ~half performance). On the positive side, if you have many (preferably independent) threads you'll often get both better throughput and better system response/latency (more "processors" available for the kernel to schedule on). ==================== Thanks! I'll have to speak with our calc-chemists about this. Perhaps there is something to be gained here performance-wise. -- /Sorin
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