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reaper
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Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 2:20 pm

I found a tip describing how to drastically decrease CPU load in Dynamips. It includes tweaking of the idlemax value. Please check out http://bit.ly/mfazKC. Sorry for crossposting but I don't feel like writing the whole thing over here and I thought it would be nice to share this.
http://lostintransit.se

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Vito_Corleone
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 2:37 pm

Hmm. So this works in conjunction with the idlepc stuff? How well did it work for you?
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routerdork
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 2:42 pm

That's interesting. I will have to test that out when I get a chance.

reaper
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 2:50 pm

Vito_Corleone wrote:Hmm. So this works in conjunction with the idlepc stuff? How well did it work for you?


Yes, from 95-100% to 20-40% on a full INE topology.
http://lostintransit.se

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wirerat
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 2:51 pm

I just left a comment over there and I'll say the same thing here. The BGP lab I posted up here a while back could never fully run on my PC at work without dynamips crashing at about the 18th or 19th router loading. I just put in the idlemax value and it all loaded and the CPU maxes out at around 30%. Definitely works for windows. Will see what does on Linux when I get home.

:cheers: to Reaper and whomever it was he mentions he found it from.
"See packet, be packet, you are packet. Ignore all else!" -The Networker
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mellowd
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:09 pm

Interesting indeed. My quick BGP lab (8 routers, GNS3 local with remote ubuntu Hypervisor) - Was running at 40% CPU across 4 cores now running at near 5%

CCIE topology running with local dynagen on ubuntu and remove dynamips on ubuntu server. - Was running at 65% across 4 cores, now running at less than 20% across all cores.


Wow, amazing change. Does this affect the stability and/or function at all?

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swagger
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:13 pm

Im not seeing the same results :/ It was rougly 20% (just for dynamips) with idlepc and roughly 20% now with idlemax :(

reaper
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:15 pm

Don't know about stability yet, just ran a few quick pings and saw nothing. Saw no flapping links or anything. Will have to try it with some more protocols enabled. If you run into anything please post here so everyone can see it.
http://lostintransit.se

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mellowd
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:15 pm

I'll modify all my .net files to use it. I'll then lab as normal and see what happens, if anything

reaper
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:17 pm

swagger wrote:Im not seeing the same results :/ It was rougly 20% (just for dynamips) with idlepc and roughly 20% now with idlemax :(


Interesting, what IOS version are you running?
http://lostintransit.se

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mellowd
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:18 pm

I'm using a combination of 3725 and 7200's btw, and it definitely worked for me

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mellowd
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:24 pm

Something more to add. Without the value, my Athlon II X4 runs all cores at full speed. Obviously using up a lot of power.

Currently all cores are running only at 800MHz - so scaled all the way down. Not only that, but CPU usage is still only 25%


Code: Select all
darreno@ubuntu10:~$ more /proc/cpuinfo | grep MHz
cpu MHz      : 800.000
cpu MHz      : 800.000
cpu MHz      : 800.000
cpu MHz      : 800.000
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wirerat
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 3:40 pm

BGP lab on Linux went down from 75% to about 37%. I wonder why this has not been widely known until now.
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Re: Drastically decreasing CPU load in Dynamips

Mon May 16, 2011 4:21 pm

Sounds really interesting
Good Luck,

David

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DanC
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Drastically decreasing CPU load in Dynamips

Tue May 17, 2011 1:38 am

Thanks or the link, will for the a whirl later on and post the outcome :)


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swagger
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Re: Drastically decreasing CPU load in Dynamips

Tue May 17, 2011 11:43 am

I'm using 3660's with c3660-i-mz-124-13b... Wondering why I'm not seeing better results :(

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Re: Drastically decreasing CPU load in Dynamips

Tue May 17, 2011 1:26 pm

Thank you for this very helpful information!

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routerdork
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Re: Drastically decreasing CPU load in Dynamips

Tue May 17, 2011 3:23 pm

I don't get anything on our setup at work. Could be because I set the system up to use on one Virtual CPU. Not a huge issue though. We use it only to lab changes.

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Re: Drastically decreasing CPU load in Dynamips

Sat May 21, 2011 10:08 am

I want to thank you again, Reaper. This should be stickied or something. I was able to gain about 2%-5% on each router in the scenario I tested. Multiplied by the number of routers this becomes a significant difference in large topologies.
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mellowd
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Re: Drastically decreasing CPU load in Dynamips

Sun May 22, 2011 4:58 am

Stickied. It's a pretty awesome setting

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