- From: Zhiheng Wang <zhihengw@google.com>
- Date: Tue, 12 Apr 2011 16:36:15 -0700
- To: Nic Jansma <Nic.Jansma@microsoft.com>
- Cc: James Simonsen <simonjam@chromium.org>, Boris Zbarsky <bzbarsky@mit.edu>, "public-web-perf@w3.org" <public-web-perf@w3.org>
- Message-ID: <BANLkTi=OKNBX-Wp_Z1w3soewV4moD+iLTQ@mail.gmail.com>
We can add a new section 4.7 for this. It would probably be non-normative recommendation. Oh, yes, I am also in favor of Boris' proposal of having a wall-clock + monotonic clock solution. cheers, Zhiheng On Tue, Apr 12, 2011 at 3:20 PM, Nic Jansma <Nic.Jansma@microsoft.com>wrote: > IE currently calculates the timestamps as Boris describes. > > > > We'd support a change in the spec to recommend this approach, though > picking simple wording to describe it may be tricky. > > > > - Nic > > > > *From:* public-web-perf-request@w3.org [mailto: > public-web-perf-request@w3.org] *On Behalf Of *James Simonsen > *Sent:* Tuesday, April 12, 2011 2:28 PM > *To:* Boris Zbarsky > *Cc:* public-web-perf@w3.org > *Subject:* Re: Timing API issues with wall-clock time > > > > On Tue, Apr 12, 2011 at 1:47 PM, Boris Zbarsky <bzbarsky@mit.edu> wrote: > > On the other hand, an issue with monotonic clocks is that you can't really > use them to record "the time right now" except in some sort of opaque > timestamp format. They're very good for measuring time intervals, of > course. Are people ok with exposing opaque timestamps (that can't > necessarily be converted to wall-clock time, etc) to JS? > > > > A few of us had a brief discussion about it at lunch today and everyone > seemed to like it. People were using the terms "monotonic clock" and > "document time." > > > > For the particular case of navigation timing one possibility is that the > page load start is recorded as wall-clock epoch time and the other times > reported by the interface are defined in terms of a monotonic clock > measuring time elapsed from the page load start. That would be > API-compatible with the existing spec, I think, but ensure that the > differences between the reported numbers actually correspond to elapsed > durations. > > > > That should be pretty safe for Navigation Timing, since all of the times > should be relatively close to the epoch time. I'm a little more concerned > about Resource Timing and User Timing, particularly on long running apps > like e-mail. The values returned by the API and the values returned by Date > could diverge quite a bit. For the longer lasting APIs, I think we need to > make it more clear we're using a monotonic clock. And it'd be nice to use > the same solution for all 3 timing APIs. > > > > James >
Received on Tuesday, 12 April 2011 23:37:00 UTC