981098 - Investigate reader mode effects on power consumption

Status: RESOLVED INVALID

(Firefox for Android Graveyard :: General, defect)

Description

[Brian Nicholson (:bnicholson)]

Since we're investigating ways to reduce power consumption, it would be useful to see what effect reader mode has. To detect if a page is readable, we:
1) Fire a web worker
2) Send a string of the entire HTML document to that worker
3) Parse the string into a DOM(ish) representation using JSDOMParser
4) Perform a number of complex algorithms on this result

We go through these steps for every page visited, so it's possible that reader mode could be consuming a non-trivial amount of power.

Comment 1

[:Margaret Leibovic]

Things have changed since this bug was filed, and (luckily!) we no longer do all this work on each page load. We only fire up a web worker and do the parser when the user taps the reader view button.

We only call the `isProbablyReaderable` function on each page load:
http://mxr.mozilla.org/mozilla-central/source/toolkit/components/reader/ReaderMode.jsm?force=1#120

Comment 2

[Nicholas Nethercote [inactive]]

Margaret, are confident that the cost is small enough that we can close this bug? (I don't mind either way and am happy to defer to your decision.)

Comment 3

[:Margaret Leibovic]

(In reply to Nicholas Nethercote [:njn] from comment #2)
> Margaret, are confident that the cost is small enough that we can close this
> bug? (I don't mind either way and am happy to defer to your decision.)

I tried digging into our telemetry data to see how often users try loading pages in reader view, and I couldn't find a probe for that, so I filed bug 1204896. I imagine that people load pages in reader view a lot less often that they load normal pages, so there are probably other power consumption bugs that would be higher priority.

I also don't know what we would do to reduce the cost of parsing a page when a user requests it.

I think bnicholson filed this bug because we used to do this on every page load, so now that that's not the case, I'll just close this out.