Code cache

[Alex Aisinzon]

Hi Eric

I thank you for the feedback. I will give this tuning a try.
I have explored another approach: I have added the option -XX:+PrintCompilation to track code compilation.
This option is not very documented. I could infer that, without a larger code cache, about 11000 methods were compiled before hitting the issue.
When using a much larger cache (512MB), I saw that about 14000 methods were compiled. 
My understanding is that the code cache is 48MB for the platform I used (x64). A 14000/11000*48MB aka 61MB cache is likely to avoid the issue. I have started a performance test with a 64MB code cache to see if that indeed avoids the code cache full issue.
If so, I would have a method to find the right code cache size. 
I will report when I have the results. I will also report if -XX:+UseCodeCacheFlushing option provides similar results to the larger code cache.

As for your question on why our app is hitting this issue: our applications has become heavier in its use of compiled code so this is likely the consequence of that. 

Best

Alex A

-----Original Message-----
From: Eric Caspole [mailto:eric.caspole at amd.com] 
Sent: Thursday, April 12, 2012 12:26 PM
To: Alex Aisinzon
Cc: hotspot-gc-use at openjdk.java.net
Subject: Re: Code cache

Hi Alex,
You can try -XX:+UseCodeCacheFlushing where the JVM will selectively  
age out some compiled code and free up code cache space. This is not  
on by default in JDK 6 as far as I know.

What is your application doing such that it frequently hits this  
problem?

Regards,
Eric


On Apr 12, 2012, at 3:15 PM, Alex Aisinzon wrote:

> Any feedback on this?
>
>
>
> Best
>
>
>
> Alex A
>
>
>
> From: Alex Aisinzon
> Sent: Monday, April 09, 2012 11:38 AM
> To: 'hotspot-gc-use at openjdk.java.net'
> Subject: Code cache
>
>
>
> I ran performance tests on one of our apps and saw the following  
> error message in the GC logs:
>
> Java HotSpot(TM) 64-Bit Server VM warning: CodeCache is full.  
> Compiler has been disabled.
>
> Java HotSpot(TM) 64-Bit Server VM warning: Try increasing the code  
> cache size using -XX:ReservedCodeCacheSize=
>
>
>
> I scaled up the code cache to 512MB (- 
> XX:ReservedCodeCacheSize=512m) and markedly improved performance/ 
> scalability.
>
>
>
> I have a few questions:
>
> *         Is there a logging option that shows how much of the code  
> cache is really used so that I find the right cache size without  
> oversizing it?
>
> *         What factors play into the code cache utilization? I  
> would guess that the amount of code to compile is the dominant  
> factor. Are there other factors like load: I would guess that some  
> entries in the cache may get invalidated if not used much and load  
> could be a factor in this.
>
>
>
> I was running on Sun JVM 1.6 update 30 64 bit on x86-64.
>
>
>
> Best
>
>
>
> Alex A
>
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