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Re: [UserTiming] Unifying marks and measures

From: Zhiheng Wang <zhihengw@google.com>
Date: Wed, 18 May 2011 12:53:14 -0700
Message-ID: <BANLkTi=5j9dzSwty-QsbH3nFyuaY6TyBKw@mail.gmail.com>
To: Tony Gentilcore <tonyg@google.com>
Cc: public-web-perf@w3.org
   Thanks, Tony. I like this. It's simple yet caters the most common
usages.

On Wed, May 18, 2011 at 4:44 AM, Tony Gentilcore <tonyg@google.com> wrote:

> As discussed on last week's call, here's one way to tie marks and measures
> into the same concept while still preserving the functionality of both. It
> largely boils down to semantics.
>
> *Overview*
>
> void mark(in DOMString name);
>

   Can we also support a given timestamp as optional input? e.g.,
    void mark(in DOMString name, in optional unsigned long long timestamp);


> unsigned long long markEnd(in DOMString name);
>

   Similar to the current measure(), shall we expand this interface to
something like:
    unsigned long long markEnd(in DOMString start_mark, in optional
DOMString name, in optional DOMString end_mark);



> Object getMarks(in optional DOMString name);
> void clearMarks(in optional DOMString name);
>
> *Examples to illustrate behavior*
>
> 1. Measure something:
>
> mark("sleep3");
> sleep(3);
> markEnd("sleep3");
> > 3
> getMarks()
> > { "sleep3": [ { "t": 1305712151745, "dur": 3 } ] }
>

     I wonder if there are better key for "t" and "dur"...


>
> 2. Clear everything:
>
> clearMarks()
> getMarks()
> > { }
>
> 3. Create a new mark:
>
> mark(performance.MARK_FULLY_LOADED)
> getMarks()
> > { "fullyLoaded": [ { "t": 1305712151745 } ] }
>
> 4. Improper usage (no start):
>
> clearMarks()
> markEnd("doesNotExist")
> > 0
> getMarks()
> > { }
>
> 5. Improper usage (end twice):
>
> mark("doubleEnd")
> sleep(2);
> markEnd("doubleEnd")
> > 2
> sleep(2);
> markEnd("doubleEnd")
> > 4
> getMarks()
> > { "doubleEnd": [ { "t": 1305712151745, "dur": 4 } ] }
>
> *Advantages over current draft*
>
> 1. To get the all data, analytics scripts only need to call one method
> (getMarks) rather than two (getMarks+getMeasures).
>
> 2. Previously measures weren't strongly tied to marks so a timeline
> couldn't be reconstructed without knowledge of the page.
>
> Consider the old case:
> mark("foo");
> mark("foo");
> measure("bar", "foo");
> getMarks();
> > { "foo": [1305712151745, 1305712151747] }
> getMeasures();
> > { "bar": [1] }
>
> Based only on the getMarks+getMeasures data, the "bar" measure cannot be
> placed on a timeline because it isn't known which "foo" it is associated
> with (or even that it is associated with "foo" at all).
>
> Now the new case:
> mark("foo");
> mark("foo");
> markEnd("foo");
> getMarks();
> > { "sleep3": [ { "t": 1305712151745 }, { "t": 1305712151747, "dur": 1 } ]
> }
>
> The getMarks() data now allows complete reconstruction of the timeline.
>

   yay, this seems to be a big plus to me.

cheers,
Zhiheng



>
> 3. There is no ambiguity about clearing marks vs clearing measures.
>
> Consider the old case:
> mark("foo")
> measure("bar", "foo")
> clearMarks("foo")
> // At this point, it may be unclear to the user what getMeasures() should
> return. Since bar is based on foo and foo was cleared: does that mean bar is
> now associated with fetchStart or has it been cleared or is it still
> associated with foo even though foo is gone? I believe we intend the 3rd,
> but I'm not sure that would be obvious to users.
>
> 4. Simpler to use as there is only one verb "mark" and fewer methods to
> understand. Each method now takes just one argument that is the same across
> all methods. Previously, it wasn't at all obvious what to pass to measure()
> and in what order without looking it up.
>
> Thoughts?
>
> -Tony
>
Received on Wednesday, 18 May 2011 19:53:39 GMT

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