1081924 - negative firstPaint value in telemetry pings

Status: RESOLVED FIXED

(Toolkit :: Telemetry, defect, P1)

Description

[Roberto Agostino Vitillo (:rvitillo)]

I have encountered few negative firstPaint values when analyzing telemetry submissions from Release (about one every 20000 submissions). Irving, do you have by chance an idea of why that might happen?

Comment 1

[:Irving Reid (No longer working on Firefox)]

For firstPaint I don't have any specific ideas; those values are recorded by StartupTimeline (http://dxr.mozilla.org/mozilla-central/source/toolkit/components/startup/StartupTimeline.h#15), so the next step would be to check if those values are reported by subtracting two time stamps, and whether those time stamps are affected by system clock adjustments (JS Date.now() is, for example).

Comment 2

[Chris H-C :chutten]

0.0016847% of main_summary pings received on 2018-08-01 had either simpleMeasurements' firstPaint or the scalar timestamps.first_paint with a value less than 1. (The scalar is a uint so negative values would be clamped to 0)

This is nicely below the noise threshold so I think we can ignore it.