[CentOS] HT (Hyper Threading) on CentOS 5.5
sorin.srbu at orgfarm.uu.se
Fri Mar 9 10:20:44 UTC 2012
From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On Behalf
Of Peter Kjellström
Sent: den 9 mars 2012 11:05
To: centos at centos.org
Subject: Re: [CentOS] 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
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.
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