Perplexing GC Time Growth

[Jason Vasquez]

Hi Ramki,

Sorry for the delay, I'm on vacation visiting some family over a long  
weekend, trying not to draw the wrath of my wife for stealing time  
away hopping on the VPN to check things out :)

Anyway, I've attached the latest garbage log, unfortunately, it  
doesn't seem to have changed things much (although I can see that the  
flags are now taking affect)

-jason

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On Jan 4, 2008, at 14:54 , Y Srinivas Ramakrishna wrote:

> Hi Jason -- did you get a chance to check what happens to scavenge
> times with both the class unloading options specified as stated below.
>
> thanks!
> -- ramki
>
> ----- Original Message -----
> From: Y.S.Ramakrishna at Sun.COM
> Date: Thursday, January 3, 2008 4:10 pm
> Subject: Re: Perplexing GC Time Growth
> To: Jason Vasquez <jason at mugfu.com>
> Cc: hotspot-gc-use at openjdk.java.net
>
>
>> Hi Jason --
>>
>> Y.S.Ramakrishna at Sun.COM wrote:
>> ...
>>> While we think of potential reasons for this, or mull over
>>> appropriate sensors that can lay bare the root cause here,
>>> could you, on a quick hunch, do a quick experiment and tell
>>> me if adding the options -XX:+CMSClassUnloadingEnabled makes
>>> any difference to the observations above. [Does your application
>>> do lots of class loading or reflection or string interning?]
>>
>> I think i screwed up a bit here. I was assuming you were using
>> the (newest) OpenJDK build. As it happens, in 6u3 and older
>> you need to specify both +CMSClassUnloadingEnabled _and_
>> +CMSPermGenSweepingEnabled, else you do not get the desired effect.
>> Sorry this was fixed after 6u3, so the additional flag did not
>> do anything in your case.
>>
>> Let me know if the additional flag (please use both) made
>> a difference, and apologies for the bad user interface here
>> (set right as of 6u4 and in OpenJDK).
>>
>> -- ramki
>>
>>>
>>

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