Default performance on Sun T5440

[jeff.lloyd at algorithmics.com]

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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