Leon Rosenberg wrote:
> Ok, my fault,
> read "page" and "java" in one sentence -> map to Java Page -> Java
> Server Page. Must be a circuit error in the brain.
> Anyway, does it mean, that a proper configured JVM on an opteron
> processor, will be significantly faster? Could be very interesting for
> caches...

It depends on the number of memory pages your memory controller has to
manage. I don't know the details about Opteron TLB (and didn't read the
article carefully enough). So if your working set size is small I doubt
any positive impact. If you use large memory/CPU the difference might be
noticable.

Modern CPUs have on chip performance counters to find out. I know, that
at least from a SPARC chip you can get the number of TLB misses from on
chip performance registers (using cpustat/cputrack under Solaris).
cpustat works for Opteron on Solaris 10 x86 too. Under Linux there seems
to be perfctr patches (see:
http://www.rz.rwth-aachen.de/computing/events/2006/sunhpc_2006/05_Smith.ppt)

Opteron has a lot of performance counters. You will find the ones
supported by cpustat on

http://opensolaris.org/os/community/observability/hardware/cpc/

> Leon
>
> On 4/3/06, Rainer Jung <tomcat-user@(protected):
>> Using large pages to eliminate TLB misses has nothing to do with the
>> size of the objects. From the view of the operating system java heap is
>> just a huge and continuous chunk of memory. Anything what's inside is
>> managed by the JVM. But whenever the JVM needs to access an adress it
>> needs to make an address calculation as described in the article. Once
>> the needed adress translation tables do not fit into the TLB,
>> performance gets bad. Since Java often uses a large and continuous heap
>> it's a very good candidate for using large pages, saving entries in the TLB.
>>
>> Leon Rosenberg wrote:
>>> Hi,
>>>
>>> recently I found (ok actually our sysadmin did) this articles on the
>>> web, and wanted to share some thoughts.
>>>
>>> http://www.devx.com/amd/Article/30529
>>> http://www.devx.com/amd/Article/30785
>>>
>>> The article describes, that using opteron and large memory pages can
>>> give significant performance wins. I don't doubt this, but I doubt,
>>> that large memory pages are a real use case in the tomcat / java
>>> webapps world. At least in applications I saw there are always many
>>> small objects, tags, beans, dtos.
>

---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscribe@(protected)
For additional commands, e-mail: users-help@(protected)