We don't have a good idea of how much maintenance may take in the wild. It happens on idle but may still be an heavy task disrupting video streaming and such.

Comment on attachment 593863 [details] [diff] [review] patch v1.0 Review of attachment 593863 [details] [diff] [review]: ----------------------------------------------------------------- ::: toolkit/components/places/PlacesDBUtils.jsm @@ +90,5 @@ > else { > + // All tasks have been completed. > + // Telemetry the time it took for maintenance, if a start time exists. > + if (aTasks.telemetryStart) { > + try { remove the try/catch, unnecessary. @@ +92,5 @@ > + // Telemetry the time it took for maintenance, if a start time exists. > + if (aTasks.telemetryStart) { > + try { > + Services.telemetry.getHistogramById("PLACES_IDLE_MAINTENANCE_TIME_MS") > + .add(Date.now() - aTasks.telemetryStart); should clear the telemetryStart value. @@ +138,5 @@ > this.checkIntegrity > , this.checkCoherence > , this._refreshUI > ]); > + tasks.telemetryStart = Date.now(); please add underscore since it's fake-private. here and elsewhere.

with fixed comments https://hg.mozilla.org/integration/mozilla-inbound/rev/a31efbfbba7b