Hi,
Do we need HT enabled on CentOS release 5.5 (Final) and Kernel Version :- 2.6.18-194.el5 Please help me understand the pros and cons of having HT enabled or disabled on the Server Dell R 710.
cat /proc/cpuinfo -> http://fpaste.org/K2dT/
Do let me know if anyone needs more information.
Regards,
Kaushal
On Fri, Mar 09, 2012 at 11:15:29AM +0530, Kaushal Shriyan wrote:
Hi,
Do we need HT enabled on CentOS release 5.5 (Final) and Kernel Version :- 2.6.18-194.el5
I don't think it harms anything to have it enabled, and there may be some small performance gains in some cases. I'd leave it on.
Please help me understand the pros and cons of having HT enabled or disabled on the Server Dell R 710.
cat /proc/cpuinfo -> http://fpaste.org/K2dT/
Do let me know if anyone needs more information.
Regards,
Kaushal _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of fred smith Sent: den 9 mars 2012 07:17 To: CentOS mailing list Subject: Re: [CentOS] HT (Hyper Threading) on CentOS 5.5
On Fri, Mar 09, 2012 at 11:15:29AM +0530, Kaushal Shriyan wrote:
Hi,
Do we need HT enabled on CentOS release 5.5 (Final) and Kernel Version :- 2.6.18-194.el5
I don't think it harms anything to have it enabled, and there may be some small performance gains in some cases. I'd leave it on.
=============================
What are some of the cases it would be practical/best to have it off?
I know there might be some negative performance issues with certain applications, but would you notice it in day-to-day use?
On Friday 09 March 2012 08.44.53 Sorin Srbu wrote: ...
What are some of the cases it would be practical/best to have it off?
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).
/Peter
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Peter Kjellström Sent: den 9 mars 2012 11:05 To: centos@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 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.
On 03/08/2012 11:45 PM, Kaushal Shriyan wrote:
Hi,
Do we need HT enabled on CentOS release 5.5 (Final) and Kernel Version :- 2.6.18-194.el5 Please help me understand the pros and cons of having HT enabled or disabled on the Server Dell R 710.
cat /proc/cpuinfo -> http://fpaste.org/K2dT/
Do let me know if anyone needs more information.
Hyperthreading is not enabled or disabled in CentOS ... it is something that you enable or disable on your machine in the computers BIOS settings.
If Hypertheading is enabled in your BIOS, then CentOS sees 2x the processors from your machine at boot up time.
-
fred smith -
Johnny Hughes -
Kaushal Shriyan -
Peter Kjellström -
Sorin Srbu