W3C

- DRAFT -

Web Performance Working Group Teleconference

28 Mar 2012

See also: IRC log

Attendees

Present
[Microsoft], Plh, +43.664.853.aaaa, +1.650.214.aabb
Regrets
Chair
SV_MEETING_CHAIR
Scribe
JatinderMann

Contents


<trackbot> Date: 28 March 2012

<Alois> Hi everyone

* Jatinder waves too

User Timing

Jatinder: "Throws a SYNTAX_ERR exception if either startMark or endMark argument, or both, have the same name as a PerformanceTiming attribute with a DOMHighResTimeStamp time value of 0."n

<plh> http://www.w3.org/TR/domcore/#exception-domexception

Jatinder: This exception protects from comparing against a Navigation Timing attribute that has been zero'd out due to cross-origin restrictions. If we allow this operation to occur, folks may get misleading data. I am in favor of raising an exception here, however, this isn't exactly a syntax error; this may better be a INVALID_STATE_ERR.n

plh: Would we consider this a security_err?

Jatinder: "The operation is insecure" doesn't sound accurate.

<plh> INVALID_ACCESS_ERR

<plh> "The object does not support the operation or argument. "

Alois: I think invalid_access_err should be the one. Because it is something that isn't supported.

James: We can just throw this one out there and see how folks react.

Jatinder: "Throws a SYNTAX_ERR exception if the duration (the end mark DOMHighResTimeStamp time value minus the start mark DOMHighResTimeStamp time value) is negative."n

The reason behind including this exception may have been to protect from comparing against a Navigation Timing attribute that has not yet loaded. E.g., performance.measure('measure1', 'navigationStart', 'loadEventEnd'), where the load event has not yet fired.

Jatinder: However, the zero case above should cover the scenario where you are measuring against loadEventEnd but the load hasn't yet fired.
... I think there is some value in being able to return negative measures. If I can do performance.measure('myMeasure', 'mark1', 'mark2') and getting all measures returns [5.0], then performance.measure('mymarkInverse', 'mark2', 'mark1') should return [-5.0].n

James: I think the negative case should be fine.

Jatinder: Sigjborn had feedback on whether we should even use exceptions.

James: plh, do we know if exceptions are still commonly used?

plh: Yes, they appear to be.

James: Between exceptions and negative numbers, I think we should just use exceptions.

High Resolution Time

Jatinder: There was feedback on whether we should change the resolution. We can either create an attribute that describes the User Agent's minimum resolution or change the recommended resolution.nnnWe change the spec text to say "MUST" return microsecond resolution. If hardware doesn't support millisecond resolution, or if high precision clocks are not available, then MUST return millisecond resolution. Most developers will just assume microseconds.

We can either create an attribute that describes the User Agent's minimum resolution or change the recommended resolution.nnnWe change the spec text to say "MUST" return microsecond resolution. If hardware doesn't support millisecond resolution, or if high precision clocks are not available, then MUST return millisecond resolution. Most developers will just assume microseconds. Those that want to check can always

scribe: or we can add an attribute that describes the resolution.

Alois: I have had to do similar research on resolution of different systems, and I recommend that we shouldn't surface those complexities to the web platform. I recommend we don't add the attribute.

plh: We should add a "SHOULD" requirement in the spec and add a note that describes the scenario where sub-millisecond clock may not be available and what developers should do to determine that.

Jatinder: Okay, I will make those changes. Also, I think we should change the minimum resolution to microseconds.

James: Agreed.

Jatinder: Another piece of feedback was that performance.now() definition should make it clear that it does not remove the time of suspension when not fully active. Seems redudant to include that considering now defines the "current" time.

James: We may want to add a note in the spec to clarify the behavior. It doesn't have to be normative.

plh: You can also add an optional test case and it doesn't have to be required.

Jatinder: I will follow up on the mailing list.

Spec Status

plh: Considering WebIDL has moved to the next stage, we expect to bring Navigation Timing to PR in April.

Jatinder: With the latest Resource Timing change, we have no remaining open items on the spec.
... With the User Timing changes, we should be able to take this spec to LC. I will email you when I have made the final changes.

Summary of Action Items

[End of minutes]

Minutes formatted by David Booth's scribe.perl version 1.136 (CVS log)
$Date: 2012/03/28 17:44:04 $

Scribe.perl diagnostic output

[Delete this section before finalizing the minutes.]
This is scribe.perl Revision: 1.136  of Date: 2011/05/12 12:01:43  
Check for newer version at http://dev.w3.org/cvsweb/~checkout~/2002/scribe/

Guessing input format: RRSAgent_Text_Format (score 1.00)

No ScribeNick specified.  Guessing ScribeNick: JatinderMann
Inferring Scribes: JatinderMann
Default Present: [Microsoft], Plh, +43.664.853.aaaa, +1.650.214.aabb
Present: [Microsoft] Plh +43.664.853.aaaa +1.650.214.aabb

WARNING: No meeting chair found!
You should specify the meeting chair like this:
<dbooth> Chair: dbooth

Found Date: 28 Mar 2012
Guessing minutes URL: http://www.w3.org/2012/03/28-webperf-minutes.html
People with action items: 

[End of scribe.perl diagnostic output]