979916 - OMTC Windows: slightly higher power usage

Status: RESOLVED WONTFIX

(Core :: Graphics, defect)

Description

[Roberto Agostino Vitillo (:rvitillo)]

When running a Youtube HTML5 video using layers.offmainthreadcomposition.enabled and layers.acceleration.force-enabled I got the following power profile on Windows:

With OMTC: CPU: 1.5W, GPU: 0.5
Without OMTC: CPU: 1.2, GPU: 0.5

Comment 1

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Probably not surprising -- before OMTC, everything was happening in one thread/core, in lockstep.  With OMTC, there is more parallelism and we're likely able to actively use two cores much more often.. so I can see a CPU power usage increase.

Comment 2

[Benoit Girard (:BenWa)]

We wont ship without tiling so it's worth waiting for tiling before investigating this too much.

I don't know if I buy the 1 core vs. 2 cores argument. Without OMTA/APZC we will be running nearly sequentially. And I'm going to assume that all other things being equal if we move run work in parallel we will drain less power overall then if ran all that work serially. We should aim to use the specialized hardware, hurry up and go to sleep ASAP.

A big change with OMTC is our layer synchronization overhead between the threads. This will chance drastically with tiling.

Comment 3

[Nicholas Nethercote [inactive]]

OMTC has shipped, so this bug isn't serving a useful purpose any more.