Re: CPU usage quirk with multiple tomcat instances

> Hello Dan,
>
> what also may happening is that you have unneeded or errorneous
> synchronisation somewhere in your code. Two instances : less code in
> same block and vm, effectively less synchronization.
>
> try to profile whether some use cases take longer on the single tomcat
> per machine.
>
> We once tried to run multiple tomcats on one machine and the results
> where opposed to yours: less performance, so i think your app behaves
> "funny" :-)
>
> regards
> Leon
>
>
> On Fri, May 2, 2008 at 2:42 PM, Lists <lists@...> wrote:
>> Hi,
>>
>>  We have a Tomcat app that is loadbalanced by hardware.  I have 4 boxes
>>  available in our test env, all of which vary slightly but not massively
>> in
>>  spec.
>>
>>  Anyway I moved from 2 tomcat instances on each machine ( listening on
>>  different ports ) down to 1 and I noticed for the same load the cpu
>>  utilisation dropped by 20%.  Interesting, how can this be explained?  Is
>>  this the extra effort in tomcat or something?  Or is it memory related?
>> the
>>  2 instances had 1gb each, and the single one has been given 4gb.
>> However I
>>  have jprofiled the instance and it has never seemed memory hungry.
>> Anyway I
>>  suspect even at 2gb for 1 instance it would still be 20% less cpu - i
>> can
>>  always do a run to prove this if people think that necessary..
>>
>>  Another thing i've found is that on one server I have abnormally high
>> CPU
>>  utilisation for the same load.  I've checked the logging levels are all
>> the
>>  same as are the java VM and the VM config settings.  I wonder what else
>>  could cause this?  All i can think is some sort of OS or hardware
>>  malfunction! maybe the CPU cache is duff or something.
>>
>>  Many thanks to any input to my Friday weird-ness!
>>  Dan
>>
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