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Context Switches - What is it / Should I concern myself with it

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Can anyone tell me what Context Switches are and how important it is in a vSphere 4.1 environment?

Is this something I need tobe deeply concerned with?

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Expert
Expert

No I did not use cirba. I used platespin power recon on my own, but cirba is one legal ahead than platespin.

I have my own rating. I choose platespin, because it easy to implemetent and i can do it on my own.

VMware Capacity Planner you can not do on your own. Cirba I don't kown you complex it is to install, about I know that IBM and Unisys

are using is. On the platespin projects I put 20-30 % onto of the platspin capacity reports, because cirba find at another platespin customer that they need 50 % more capacity than the platespin reported. They found that the mostly it had to do with context switches.

1.) Cirba

2.) Platespin

3.) VMware

A good articel to context switches comes from this url:

http://www.thomaskoetzing.de/index.php?option=com_content&task=view&id=196&Itemid=260&lang=en

http://ict-freak.nl/2008/02/15/perfomance-monitoring-and-context-switches/

Context Switches/sec (System)

0-10,000 ( > 10,000 may indicate too many threads contending for resources; correlate with System Calls/sec and threads counter in Windows Task Manager to identify process responsible)

If you buy the latest cpu generations of Intel or AMD this help to reduce context switches.

But against a bad application like the following example you have no chance.

http://techdigger.wordpress.com/2009/07/13/page-faults-and-context-switches-chrome-flash-and-techcru...

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Immortal
Immortal

http://en.wikipedia.org/wiki/Context_switch

Where do you read about that regarding ESX 4.1?


AWo

VCP 3 & 4

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Hi AWo,

We are in the early stages of a virtualization migration project and a consultant here mentioned that he wanted to run his own capacity planner tool (It is a thrid party tool) becuase he said the VMware capacity tool does not go deep enough, and his example was context switching. So I am struggling with what this is and should I really be concerned. My gut feeling is that the VMware capacity tool is sufficent for our environement. Is this something you have come across?

Thanks for the link on context switching.

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Immortal
Immortal

No, I didn't work with the VMware Planner for a long time. The last time I did such a project we used PlateSpin's (today Novell) PowerRecon.

That was offered for a project price (x$ per server per day) and at this time (2005) it was better than the Capacatiy Planner.

I don't know how it works today....


AWo

VCP 3 & 4

\[:o]===\[o:]

=Would you like to have this posting as a ringtone on your cell phone?=

=Send "Posting" to 911 for only $999999,99!=

vExpert 2009/10/11 [:o]===[o:] [: ]o=o[ :] = Save forests! rent firewood! =
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Expert
Expert

The articel is a bit older but still valid. It would be interessing which step ahead Intel and AMD made in this direction.

WHich Tird PArty Capacity Planner is being used? Platespin or Cirba?

http://www.google.de/url?sa=t&source=web&cd=3&ved=0CCgQFjAC&url=http%3A%2F%2Fcommunities.vmware.com%...

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Enthusiast
Enthusiast

Hi Meistermn,

The capacity planner tool was Cibra. Do you have any experience with this product?

Thanks for the added info.

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Expert
Expert

No I did not use cirba. I used platespin power recon on my own, but cirba is one legal ahead than platespin.

I have my own rating. I choose platespin, because it easy to implemetent and i can do it on my own.

VMware Capacity Planner you can not do on your own. Cirba I don't kown you complex it is to install, about I know that IBM and Unisys

are using is. On the platespin projects I put 20-30 % onto of the platspin capacity reports, because cirba find at another platespin customer that they need 50 % more capacity than the platespin reported. They found that the mostly it had to do with context switches.

1.) Cirba

2.) Platespin

3.) VMware

A good articel to context switches comes from this url:

http://www.thomaskoetzing.de/index.php?option=com_content&task=view&id=196&Itemid=260&lang=en

http://ict-freak.nl/2008/02/15/perfomance-monitoring-and-context-switches/

Context Switches/sec (System)

0-10,000 ( > 10,000 may indicate too many threads contending for resources; correlate with System Calls/sec and threads counter in Windows Task Manager to identify process responsible)

If you buy the latest cpu generations of Intel or AMD this help to reduce context switches.

But against a bad application like the following example you have no chance.

http://techdigger.wordpress.com/2009/07/13/page-faults-and-context-switches-chrome-flash-and-techcru...

View solution in original post

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Expert
Expert

Cirba and context switching:

Profile workloads to uncover dangerously dangerous context switching levels or suspicious CPU utilization levels, runaway processes, high I/O, or other profiles that could be problematic

http://www.cirba.com/resources/US-Federal-Data-Center-Consolidation-Initiative.htm

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Immortal
Immortal

Context switching is something the be aware of (although dangerous levels are rare, esp. with modern CPUs). Is your consultant wanting to charge you for it?

--Matt

VCP, VCDX #52, Unix Geek, Storage Nerd

9773_9773.gif

--Matt VCDX #52 blog.cowger.us
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Enthusiast
Enthusiast

Yeah, the conslutant wants to charge for the engagmenet. I'll have to make a decision soon.

Thanks for your help.

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Expert
Expert

How big is your environment ?

Maybe I found another for free.

http://www.lanamark.com/product/overview

Free IT asset discovery, search and business-centric reporting - no time limits

Identify consolidation, virtualization and other cost-reduction opportunities from the desktop to the data centerEngage top IT solution providers leveraging Lanamark Suite Services Edition to help you make strategic IT infrastructure investments

Lanamark enabled SJ Berwin to quickly identify server consolidation opportunities and justify the benefits of virtualization.”

Enthusiast
Enthusiast

If you've engaged a consultant to assist you with your consolidation assessment, it's usually best to let them use the tool they are most familiar with - and thus get the best result.

If they want to charge you extra for licensing the tool where a free or cheaper tool would be sufficient for the environment, that's certainly something to take into account. Depending on the size and complexity of your environment, it may be warranted.

As for context switching, you'll find a lot of good discussion of it's impact around Terminal Services for Windows, and Citrix - environments where having oodles of processes all competing for processor time is quite common. As was said above, it's not common for it to be an issue in your average application server environment.

Enthusiast
Enthusiast

Thanks guys for all the great insight !

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