Re: Isn't it time to make libxslt multi-threaded?

On 26/07/2012 16:32, Дмитрий Грибов wrote:
>     Yes, due to the functional nature of XSLT, xsl:for-each and
>     xsl:apply-templates can be parallelized automatically. It would make
>     for an interesting project, but I doubt you'll find someone who
>     wants to implement this on top of libxslt. I think that most users
>     of libxslt don't need lower latency for processing of a single
>     stylesheet.
>
> And that's strange, I tell you. I've seing some laggy xslt-based sites
> and one of the most importaint problems with xslt on the web is
> performance and responsivness.

Quite a while ago, I did extensive performance comparisons of many Perl 
based templating solutions and I found libxslt to be faster than all of 
them, at least when using compiled stylesheets. So I guess the sites 
you're talking about are doing something wrong or have performance 
problems in other areas.

>     You wrote that you process "a huge and dedicated xml". Do you by
>     chance load a large XML file with the "document" function? That's
>     the only situation where I ran into performance problems in the
>     past, because the parsed XML file won't be cached across
>     transformations.
>
> Our XML isn't that "large" to make things painfull, about 100kb - 500kb.
> And there is no way (at least I see none) to cache anything except XML
> as text fragments and then feed concatenation to "parse_string" (what we
> really do most of the time). Not too elegand, but parse_string() takes
> less than ~0.01s and I know what I'm paying for. I doubt I can get more
> of it without breaking the whole data-presentation brilliance to peaces.

Yes, with Perl I found that creating the XML input document with simple 
string concatenation and then calling parse_string() to be much faster 
than constructing the document using the DOM-like functions of libxml. 
Using this technique and compiled stylesheets, the XSLT transformation 
of a typical web page takes well below 10 milliseconds in my experience.

On the other hand, XSLT is very powerful and can easily be abused for 
things that should better be done with a real programming language.

Also note that libxslt has profiling support (see xsltproc --profile). 
That might help with optimizing your stylesheets.

Nick

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