tomcat-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jesse Klaasse <jesse.klaa...@indicia.nl>
Subject RE: Tomcat 100% CPU usage after moving from Java 5 to 6
Date Tue, 26 Jan 2010 15:50:05 GMT

Hi Chuck, thanks for your extensive comments about the JVM options.. 


n828cl wrote:
> 
>>-Xms10240m -Xmx10240m
> 
> That's a very large heap; shouldn't hurt as long as you have enough RAM to
> support it all without paging.  (But see below for use with compressed
> OOPs.)
> 

This shouldn't be a problem, the system has 16 GB RAM, almost all of it
dedicated to Tomcat.


n828cl wrote:
> 
>> Tomcat's CPU usage seems significantly lower than before 
>> (it's average seems about 10% now - which was 30-40% before)
> 
> There are some improvements in the JDK/JRE 6 JIT and synchronization
> handling, but probably not enough to account for that large a difference.
> 

Well, I don't know where exactly it's coming from, but after a full day very
closely monitoring the system, it turns out to be the truth. Which is not a
bad thing, of course :)


n828cl wrote:
> 
>> I also added the -XX:+UseCompressedOops JVM option
> 
> Be careful with that; it can impact CPU usage, since the compressed OOPs
> have to be expanded into actual pointers every time they're used, and
> pointers compressed when stored in a field.  Works best with heap sizes
> less than 4 GB, which avoids the decoding/encoding.  For a real
> explanation of compressed OOPs, look here:
> http://wikis.sun.com/display/HotSpotInternals/CompressedOops
> 

I already found that article myself. Since CPU usage is as low as it is now,
I have decided to give it a try.
Anyway, thanks again!
-- 
View this message in context: http://old.nabble.com/Tomcat-100--CPU-usage-after-moving-from-Java-5-to-6-tp27305110p27324793.html
Sent from the Tomcat - User mailing list archive at Nabble.com.


---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
For additional commands, e-mail: users-help@tomcat.apache.org


Mime
View raw message