71447 - startup loads RDF/XML files (4% of startup time)

Status: VERIFIED INVALID

(Core Graveyard :: RDF, defect)

Description

[Cathleen]

waterson done some investigaton and found that we're loading 34 RDF files.
his list is below

$(DIST)/bin/chrome/user-skins.rdf
$(DIST)/bin/chrome/all-skins.rdf
$(DIST)/bin/chrome/user-locales.rdf
$(DIST)/bin/chrome/all-locales.rdf
$(DIST)/bin/chrome/all-packages.rdf
$(PROFILE)/chrome/user-skins.rdf
$(PROFILE)/chrome/all-skins.rdf
$(PROFILE)/chrome/user-locales.rdf
$(PROFILE)/chrome/all-locales.rdf
$(PROFILE)/chrome/all-packages.rdf
$(PROFILE)/localstore.rdf
$(DIST)/bin/chrome/overlayinfo/navigator/skin/stylesheets.rdf
$(PROFILE)/chrome/overlayinfo/navigator/skin/stylesheets.rdf
$(DIST)/bin/chrome/overlayinfo/navigator/content/overlays.rdf
$(PROFILE)/chrome/overlayinfo/navigator/content/overlays.rdf
$(PROFILE)/search.rdf
$(DIST)/bin/chrome/overlayinfo/messenger/skin/stylesheets.rdf
$(PROFILE)/chrome/overlayinfo/messenger/skin/stylesheets.rdf
$(DIST)/bin/chrome/overlayinfo/messenger/content/overlays.rdf
$(PROFILE)/chrome/overlayinfo/messenger/content/overlays.rdf
$(DIST)/bin/chrome/overlayinfo/global/skin/stylesheets.rdf
$(PROFILE)/chrome/overlayinfo/global/skin/stylesheets.rdf
$(DIST)/bin/chrome/overlayinfo/global/content/overlays.rdf
$(PROFILE)/chrome/overlayinfo/global/content/overlays.rdf
$(DIST)/bin/chrome/overlayinfo/communicator/skin/stylesheets.rdf
$(PROFILE)/chrome/overlayinfo/communicator/skin/stylesheets.rdf
$(DIST)/bin/chrome/overlayinfo/communicator/content/overlays.rdf
$(PROFILE)/chrome/overlayinfo/communicator/content/overlays.rdf
chrome://global/locale/builtinURLs.rdf
$(DIST)/bin/chrome/overlayinfo/chatzilla/skin/stylesheets.rdf
$(PROFILE)/chrome/overlayinfo/chatzilla/skin/stylesheets.rdf
$(DIST)/bin/chrome/overlayinfo/chatzilla/content/overlays.rdf
$(PROFILE)/chrome/overlayinfo/chatzilla/content/overlays.rdf
chrome://communicator/locale/taskbar.rdf

hyatt claimed that most of these rdf files dont exist.  chrome registry tries to 
load many of them and failed...

what can we do to speed up this process?

Comment 1

[Chris Waterson]

Ok, profiled this. It turns out that short-circuiting the datasource creation is
not going to buy us much. The time is spent actually reading and parsing the
RDF/XML. There's an older bug that I just un-futured that we should fix instead,
which has to do with emitting terse RDF/XML (bug 35816). Resolving this as INVALID.

Comment 2

[Chris Waterson]

I should've added, RDFXMLDataSourceImpl::Refresh() is what I'm looking at; it's
the place where the time is spent. Of that, about 70% of the time is spent in
nsParser::OnDataAvailable(), consuming bytes. Very little time is spent in
nsFileChannel::Open(). A marginal amount of time is spent in the component
manager creating the parser etc.: we *could* short-circuit that if we were
willing to try to stat() the file first. (But then we pay for component creation
of nsIFile objects, etc., as well as doing a double-stat in the case where the
file exists. Seems like a wash.)

So the money is in making the RDF/XML content sink do less work.

Comment 3

[Tom Everingham]

verified