Inconsistent request timings in Network and Timeline tab
Reported by
mikolaj....@hgv-online.de,
Aug 8 2016
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Issue descriptionUserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36 Steps to reproduce the problem: I'm not sure if I can reproduce this in a public example. I can try if it's needed. What is the expected behavior? The timings should be consistent What went wrong? On the attached screenshots, the 1st one is from network tab (613ms), and the 2nd one is from timeline tab (3s). And I can tell that the timeline tab got it right, at least as far as the UI is concerned. Did this work before? N/A Chrome version: 52.0.2743.116 Channel: stable OS Version: OS X 10.11.6 Flash Version: Shockwave Flash 22.0 r0 Maybe it's not a bug, just an UX issue. I find it hard to understand why should the timings be so different.
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Aug 9 2016
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Sep 8 2016
After spending some time with it, I suppose that the timings are different because the Network tab shows the time of the actual network request, and the Timeline tab shows the time "as seen by JS", that is, until the event loop is free and can actually handle the response. So maybe it's not a bug as such, but there is some room for improvement in the UI.
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Sep 8 2016
#3 Yes, this is caused because they are different metrics. The timing in the network panel is designed to give info on what you can do to improve/diagnose network related issues. Timeline is more designed around what can be done to improve/diagnose javascript, css, html related issues. The timing from network is driven mostly from the browser process and the timings from timeline are mostly driven from the renderer process. You can get a little more info on the architecture of what I am referring here: https://www.chromium.org/developers/design-documents/multi-process-resource-loading Likely in this case the IPC was likely blocked and it must go across IPC for timeline to obtain the timings, where network panel gets it's timing from browser (before IPC). Thanks for the report though! |
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Comment 1 by kozyatinskiy@chromium.org
, Aug 9 2016