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Re: Garbage Collection Performance Hit
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Re: Garbage Collection Performance Hit


  • Subject: Re: Garbage Collection Performance Hit
  • From: Chris Espinosa <email@hidden>
  • Date: Wed, 31 Oct 2007 12:48:55 -0700


On Oct 31, 2007, at 12:19 PM, Adam R. Maxwell wrote:

On Wednesday, October 31, 2007, at 12:06PM, "Michael Watson" <email@hidden> wrote:
What have you done to make you believe this, out of curiosity? (I'd  
love to have an example of things to look for in future profiling, if  
you've got some sort of data here.)

I've sampled Xcode when the editor beachballs while I'm typing code; it's like using an ssh connection over a 1200 baud modem :).  If you're interested in actual samples, e-mail me offlist.  In the case of Xcode it also seems related to project and class file size, and I can point you to a couple of open source projects that are now painful to work with.

The collector in this case is just the poor victim of an algorithm that's going haywire on your particular source code.  Please file a bug; syntax coloring can create and dispose of a large number of ephemeral objects during parsing, and this creates a lot of garbage for the collector to clean up.  On a dual-core system this is hardly noticeable, but as you point out, single-core PPC machines do take it in the shorts.

The cure for this is not a better collector but a better parser that generates less transient data.  We made a number of tunings in this over the course of Xcode 3.0's development and we have more to do, so please file a Radar report with your source code so we can see what idioms are triggering this.

Chris
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References: 
 >Garbage Collection Performance Hit (From: Robert Martin <email@hidden>)
 >Re: Garbage Collection Performance Hit (From: Chris Espinosa <email@hidden>)
 >Re: Garbage Collection Performance Hit (From: "Adam R. Maxwell" <email@hidden>)
 >Re: Garbage Collection Performance Hit (From: Michael Watson <email@hidden>)
 >Re: Garbage Collection Performance Hit (From: "Adam R. Maxwell" <email@hidden>)

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