Re: [tor-bugs] #19276 [Applications/Tor Browser]: Scrolling is slow and CPU intensive

["Tor Bug Tracker & Wiki" <blackhole@xxxxxxxxxxxxxx>]

#19276: Scrolling is slow and CPU intensive
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 Reporter:  cypherpunks                          |          Owner:  tbb-
     Type:  defect                               |  team
 Priority:  Medium                               |         Status:
Component:  Applications/Tor Browser             |  needs_information
 Severity:  Normal                               |      Milestone:
 Keywords:  tbb-6.0-issues, tbb-usability, tbb-  |        Version:
  performance                                    |     Resolution:
Parent ID:                                       |  Actual Points:
 Reviewer:                                       |         Points:
                                                 |        Sponsor:
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Comment (by yawning):

 Replying to [comment:14 49ax56xr36]:
 > Replying to [comment:11 yawning]:
 > > Everyone that actually has the issue is leaving out "what video card
 they have, and what drivers they are using if applicable".
 >
 > nxagent -- virtual screen X-server, older version
 >
 > Don't think an actual "drivers" are in the picture here, just the screen
 virtualizing X11 NX server.

 Well, same sort of problem.  I don't think that supports any of the
 relevant acceleration methods well enough (if at all), so you're probably
 stuck on some sort of software rendering regardless.

 > Worked reasonably well with 5.5.5 and xrender=true.  Epic disaster with
 6.0.1.  Six-oh-one with xrender=false seems a bit faster than 5.5.5 with
 xrender=true, but not different enough to cause complaint.  Does seem a
 regression in the xrender code.  Reading some of the above links it
 appears xrender is a mixed proposition.  Works brilliantly on many
 targets, not-so-great on others.  Could be a dumb bug that's imperceptible
 on fast hardware.

 One thing worth looking at for your specific case is disabling the off-
 main thread compositing (Enabled in FF40, so the 6.0.x series would be the
 first Tor Browser releases to support it.  See
 https://bugzilla.mozilla.org/show_bug.cgi?id=994541).

 Try setting `layers.offmainthreadcomposition.enabled` to `false`.
 Behavior is noticeably different on my Poulsbo Atom box (using the open
 source 2D only drivers).

 Unfortunately, if I were a real Tor Browser person, I'd probably push
 against making the modified version of the pref the default even if it
 helps the 2d only configs since doing so will likely hurt more configs
 than it helps.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19276#comment:15>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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