W3C home > Mailing lists > Public > public-web-perf@w3.org > August 2012

Disparity between time bases in HighResolutionTime and ResourceTiming

From: James Simonsen <simonjam@chromium.org>
Date: Wed, 8 Aug 2012 16:42:06 -0700
Message-ID: <CAPVJQimPVAx3LWNrvCcDzMetqkeM0zNvnoAdJv9iaVU128tgcA@mail.gmail.com>
To: public-web-perf <public-web-perf@w3.org>
Resource Timing says:

"...the user agent must record the system clock at the beginning of the *
root* document navigation..."

High Resolution Time says:

"...the number of milliseconds from the navigationStart attribute of the
PerformanceTiming interface, the start of navigation of *the* document..."

So in iframes, Resource Timing will be offset, but now() won't be. That
seems bad. We should be consistent.

We went with the root document in Resource Timing intentionally. We want to
present a uniform timeline that can just be displayed, including iframe
content.

So I think we should change High Res Time to match Resource Timing's
definition.

We should define "root document" too. I think we can work the cross-origin
concerns into that: walk the parent document chain as long as there's a
parent and it has the same origin as the current document. Wherever you
stop is the root document.

James
Received on Wednesday, 8 August 2012 23:42:34 UTC

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