Matt Sergeant wrote:
On Saturday, August 24, 2002, at 07:12 PM, Nick Wellnhofer wrote:Daniel Veillard wrote:On Sat, Aug 24, 2002 at 03:13:08PM +0200, wellnhofer aevum de wrote:Hi,I'm using libxml and libxslt with Perl to generate dynamic HTML pages and did some performance testing recently. I created a XML tree from a Perl data structure using the DOM interface and transform that tree with XSLT.While the performance of the XSLT transformation is really good, I found that constructing the DOM tree took about 75% of the running time. So it takes about three times longer to create the XML source tree than to parse a stylesheet and apply and output the transformation.Is this behavior normal? I would think creating an XML tree is much faster than a XSLT transformation.Well usually when creating the input tree using directly the C parser,the parse time (which includes building the DOM tree) is quite smaller than the tranformation time itself. So no it's not "normal", though it also depends a lot on the stylesheet used too. You're probably paying the cost of going back and forth between the Perl and the C library for each call to DOM entry points.Yes, that seems to be the only explanation I can think of. The XSLT transformation needs about 5 calls to the C library, but the creation of the DOM tree requires hundreds of calls of createElement and appendChild.It might even be faster to generate XML directly in Perl and write it to a file or memory buffer and then parse it with libxml again. I think I will try that, although it seems like a stupid approach.The best solution is probably a single Perl XS function that converts a whole Perl data structure to a DOM tree in one go.Yeah, it's all the method calls, and also the memory allocation and the reference counting that the Perl level API has to do, but the C one doesn't. It *might* be quicker to do it in perl-space and create an XML string and then parse it.
I just replaced the following Perl code to create a XML element containing only text
my $child = $doc->createElement($k);
$node->appendChild($child);
my $text = $doc->createTextNode($v);
$child->appendChild($text);
with the equivalent
$node->appendTextChild($k, $v);
Building the DOM tree is now two times faster, but still a little slower
than the XSLT transformation.
Nick Wellnhofer