[Webkit-unassigned] [Bug 110779] WebKit API for enabling DOM logging for certain worlds

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=110779





--- Comment #22 from Adam Barth <abarth at webkit.org>  2013-02-27 16:18:44 PST ---
(In reply to comment #21)
> (In reply to comment #19)
> > (From update of attachment 190556 [details] [details])
> > View in context: https://bugs.webkit.org/attachment.cgi?id=190556&action=review
> > 
> > > Source/WebKit/chromium/public/WebCoverWrapping.h:54
> > > +    // Sets the provided log object for the world identified 
> > > +    // by worldID (worldID may be 0 identifying the main world).
> > 
> > I thought we weren't going to support installing a logger for the main world?
> 
> Logging can be enabled for any world. The guarantee is that the DOM bindings for all
> those worlds for which logging is not enabled would not be affected. We include the main world
> to log DOM activity inside extension background pages.

I see.  Won't you need to do the hash lookup to see if there is a logger configured for a world?  That seems like it will impact performance even if no logger is configured.

> The logger will be invoked on all DOM API calls that are covered by the policy. 
> To begin with we will have a small policy that includes critical calls like document.write, document.createElement, document.appendChild, window.location and so on.

Do you plan to teach WebKit about this policy, or does WebKit always just call the log function?  Maybe the answer to this question is related to my previous question and the issue is just that I don't understand this part of the design.

> We do not have any performance measurements at the moment but we do plan to have them in the near future. 

Would you be willing to do some performance measurements before landing this patch?  The performance aspects are an important consideration here.  I would be interested in knowing the overhead for the following cases:

1) No logging configured for world.
2) Logging configured for world, but the API is not logged according to the policy.
3) Logging is configured for world, and the API is actually logged.

In particular, I'm curious how this affects Dromeo's dom-traverse benchmark in these cases.  You can find dom-traverse in the PerformanceTests directory.  You can find more information about PerformaceTests on this wiki page:

http://trac.webkit.org/wiki/Performance%20Tests

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