Default performance on Sun T5440

[Jon Masamitsu]

Jeff,

This might be something different.  First what jdk are you using?
What's you command line?  If you are using CMS, can you
try a run with -XX:-UseParNewGC?  If not using CMS, can
you try -XX:+UseSerialGC (assuming you're using jdk5 or
later).

Jon

jeff.lloyd at algorithmics.com wrote On 10/02/09 10:56,:

>Hi John,
>
>Thanks for responding.  However I just want to show you a simple gc
>without manually setting the number of gc cpus:
>
>178.427: [GC 178.427: [ParNew: 471872K->52416K(471872K), 18.8885468
>secs] 1054705K->756342K(12530496K), 18.8895357 secs] [Times: user=740.49
>sys=15.54, real=18.89 secs]
>
>Compared to a similar gc when I set the max parallel cpus to 8:
>
>170.531: [GC 170.532: [ParNew: 118014K->13056K(118016K), 0.1646787 secs]
>863713K->771012K(12569856K), 0.1651373 secs] [Times: user=0.76 sys=0.05,
>real=0.17 secs]
>
>I apologize it isn't totally apples-to-apples because I reduced the YG
>from 512M to 128M, but look at the difference in "user" time.  After
>5-10 minutes of uptime my application was reporting 135 minutes of cpu
>time with the default settings.
>
>I'm not sure if this is helpful to you or the appropriate place to
>provide feedback, but this is what people are going to be seeing if they
>don't understand gc details.
>
>Jeff
>
>-----Original Message-----
>From: Jon.Masamitsu at Sun.COM [mailto:Jon.Masamitsu at Sun.COM] 
>Sent: Friday, October 02, 2009 1:40 PM
>To: Jon Masamitsu
>Cc: Jeff Lloyd; hotspot-gc-use at openjdk.java.net
>Subject: Re: Default performance on Sun T5440
>
>Jon Masamitsu wrote On 10/02/09 10:19,:
>
>  
>
>>Jeff,
>>
>>The default number of GC threads was changed to be fewer in
>>jdk6u14 (same change in jdk7). I'm guessing you're using
>>an older jdk? The number of GC threads depends on the
>>number of cores on the platform. I think on the T5440 the
>> 
>>
>>    
>>
>^^^^^^^^^^^^  cores should be strands
>
>  
>
>>number will be about 3/16 * 256 or 48.
>> 
>>
>>    
>>
>
>This is still correct.
>
>
> 
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