[higgins-dev] Re: Bottleneck points in PDS service

[Sergey Lyakhov <slyakhov@xxxxxxxxxxxxxx>]

Markus,

> Another thing to make sure is that the client sets the header Content-Type:
> text/xdi+x3, so that the XDI server uses the X3StandardReader instead of the
> AutoReader, but I think this is happening already.

Yes, we use this content type.

> Out of curiosity, what software did you use for profiling?
 
I've used TPTP  http://www.eclipse.org/tptp/ . 

Thanks,
Sergey Lyakhov

On Fri, 21 May 2010 19:44:13 +0200
Markus Sabadello <msabadello@xxxxxxxxx> wrote:

> Hello Sergey,
> 
> On Fri, May 21, 2010 at 4:13 PM, Sergey Lyakhov <slyakhov@xxxxxxxxxxxxxx>wrote:
> 
> > Markus,
> >
> > I've profiled/debugged PDS service and found two bottlenecks in XDI4J:
> >
> > 1. The most part of processing time takes xdi4j.xri3.impl.parser.Parser,
> > see attached 1_thread.html.
> > However this is a class generated from ABNF, and I am not sure there is a
> > way to significantly increase its performance.
> >
> 
> Yes I agree this is probably not possible..
> The only option here would be to use String instead of XRI3Segment, but this
> would have big implications on the entire library, because in some places
> the functionality of XRI3Segment is really needed.
> 
> 2. XDI has multithreading problems. The time of processing for parallel
> > threads increases linearly
> > the number of threads (see attached 5_threads.html and 10_threads.html).
> >
> > This occurs because XDIReaderRegistry contains singleton readers, which, in
> > turn, are not thread-safe and
> > contain synchronized method read(). So, all threads in
> > EndpointServlet.readFromBody() method get the same singleton
> >  instance of XDIReader from XDIReaderRegistry and wait on its read()
> > method. We can try to fix that by changing
> > XDIReaderRegistry to return a new instance of reader instead of singleton.
> >
> 
> The reason why I used singletons was that I thought it's better to re-use
> the reader objects instead of creating/destroying them all the time. But
> yes, maybe I was wrong and its better to return new instances for every read
> operation.
> 
> Another thing to make sure is that the client sets the header Content-Type:
> text/xdi+x3, so that the XDI server uses the X3StandardReader instead of the
> AutoReader, but I think this is happening already.
> 
> Out of curiosity, what software did you use for profiling?
> 
> Markus
> 
> 
> > Thanks,
> > Sergey Lyakhov