Thanks for the information. So are you firing off the requests manually,
simply by hitting the send key simultaneously on three browsers?
If four transformations run concurrently, with no contention between them,
then you would expect each one to take four times as long as when the
processor is dedicated to a single user. This seems to be consistent with
the results you observe.
In a real environment the arrival time of requests will be randomly
distributed, and there will be significant think time, so the response time
will be much better than T*N where T is the transformation time and N is the
number of users.
As the number of users increases you have a classic transaction processing
scenario. The theoretical maximum throughput you can achieve
(transformations per second) is determined by dividing the machine capacity
by the cost of each transformation. Achieving optimal response time then
depends on scheduling the work intelligently to avoid overloading the
available memory, which depends on how you configure your application
server. The ideal concurrency in this environment is probably obtained by
taking the available memory, subtracting the shared memory requirement, and
dividing what's left by the memory requirement of each transformation. Don't
ask me to translate this into concrete Websphere terms!
Michael Kay
-----Original Message-----
From: Bhupendra Singh [mailto:skbhupendra(_at_)yahoo(_dot_)co(_dot_)uk]
Sent: 01 December 2004 18:18
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: RE: [xsl] Performance with multiple users during
transformation
Michael ,
Thanks for the input, Heres what you requested for.
You need to explain your measurement scenario more
carefully. How is the
XSLT processor running - as a servlet?
The XSLT processor is running as a servlet. Its a Web
based application, which takes client request with
Servlets. The serlvet brings the data in XML format
and then uses the transformer to make another XML,
which is send back to the user.
How are you
measuring response time?
I am taking the diference of the time before and after
the Transformer.transform() method and printing it in
a log file.
Are
these transformations all
using the same stylesheet?
All the users are requesting the same page with the
same parameter, so the same input XML and stylesheet
is used.
Are you saving the
compiled stylesheet in memory?
I am storing the compiled XSLT as templates in a
Hashmap. I use this Template to create a new
Transformer object using the
templates.newTransformer().
Before taking the test I am running a dummy user
request to build this template in the Hashmap.
Are they all running in the same thread, or do you
have a pool of
threads/processes?
Each user fires the request from different IE
sessions. Thus the servlet threads will be different
for each.
how much memory you
are allocating to the Java VM,
I have kept the minimum JVM heap size to 1 GB for
Websphere App server.
--- Michael Kay <mike(_at_)saxonica(_dot_)com> wrote:
I have a 250 KB XML to be transformed into another
XMl
document. I am using a high end UNIX box with 8
CPUs
and 32 Gig RAM.
Intially I was using Xalan and the timings for
transformation are as follows:
1 user : 3 secs
2 users: 6 secs
4 users: 8 secs
Then I changed to Saxon8 and the timings are
1 user : 1.5 secs
2 users: 3 secs
4 users: 4 secs
(I fear whats going to happen when 1000 users will
use
the applicaiton)
You need to explain your measurement scenario more
carefully. How is the
XSLT processor running - as a servlet? How are you
measuring response time?
What is the think time between transactions? Are
these transformations all
using the same stylesheet? Are you saving the
compiled stylesheet in memory?
Are they all running in the same thread, or do you
have a pool of
threads/processes?
Although I got a 50% performance enhancement with
Saxon for each scenario, but I still dont
understand
one thing why do we have the increase in
transformation timing as the users increase.
That depends very much on how the work is being
scheduled, which is why I
asked about your execution environment.
Since Saxon is based on SAX parsing there should
be no
memory constrained (Also my 32 Gig RAM is never
utilised more than 5GB at any time.)
No, that's a bad misunderstanding. Every XSLT
processor today builds the
source document in memory. However, 250Kb is not
particularly big. Again,
however, it depends on how you are scheduling the
work, how much memory you
are allocating to the Java VM, and so on.
Can somebody briefly tell me how the
transformation
works, starting from how the XSL is parserd, how
the
XML is parsed and then the transformation.
Can the parser and the XSLT processors be
different.
If you're using Saxon, then the article at
http://www.xml.com/pub/r/1065 may
be helpful.
Michael Kay
http://www.saxonica.com/
--~------------------------------------------------------------------
XSL-List info and archive:
http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to:
http://lists.mulberrytech.com/xsl-list/
or e-mail:
<mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--
______________________________________________________________
__________
Yahoo! India Matrimony: Find your life partner online
Go to: http://yahoo.shaadi.com/india-matrimony
--~------------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail:
<mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--
--~------------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--