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From Bob DeRemer <bob.dere...@thingworx.com>
Subject RE: high CPU usage with NIO and 1000+ websockets on Tomcat 7.0.49?
Date Sat, 14 Dec 2013 14:15:37 GMT


> -----Original Message-----
> From: Mark Thomas [mailto:markt@apache.org]
> Sent: Saturday, December 14, 2013 9:06 AM
> To: Tomcat Users List
> Subject: Re: high CPU usage with NIO and 1000+ websockets on Tomcat 7.0.49?
> 
> On 13/12/2013 13:12, Bob DeRemer wrote:
> > We have been profiling this in YourKit and as we increase the number
> > of websockets, naturally we see the CPU utilization increase.  The
> > concern is that we're seeing this at what seems to be a fairly low
> > number of websockets.  The YourKit profiling showed 41% of the time
> > being spent in the following code.  My apologies for the formatting.
> > I can provide an attachment out-of-band if it would be helpful.
> 
> I've seen similar figures from YourKit when testing with just a single
> connection. There does seem to be a lot of time spent in the NIO Poller code.
> 
> When I looked at it last time nothing immediately obvious jumped out at me in
> terms of something that could be changed to improve things. It needs some
> more time spent on a deeper analysis. That is on my TODO list. If any NIO
> experts want to take a look and make some suggestions that would be great.
> 
> As an aside, as much as I like YourKit, you do have to be careful (as you do with
> any profiler) when stress testing that the profiler isn't distorting the results. I
> have been led down the wrong path a few times when I wasn't careful enough.
> 

I have noticed about a 20% reduction in performance using Yourkit in it's least intrusive
mode.  Thanks for the input and suggestions.  If I find out anything additional, I'll post
it.

Thx, bob

> Mark
> 
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