1349159 - JS engine slowness makes zooming in/out of SVG map of the US States less smooth than in Chrome

Status: RESOLVED INCOMPLETE

(Core :: JavaScript Engine, enhancement, P3)

Description

[Jonathan Watt [:jwatt]]

From bug 873425 comment 17.

https://bl.ocks.org/mbostock/2206340

Zooming in and out (two finger scrolling/mouse wheel) is not so smooth in Firefox on my computer as it is in Chrome.

The example doesn't implement zooming via a transform as you might expect. Instead it recalculates entirely new path data for a bunch of SVG <path> elements that are the outlines of each US State, setting the path data on the elements by calling setAttribute('d', ...).

Profile: https://perfht.ml/2mPTc8k

  7802 ms  100%  under load
  7200 ms   92%  JS::Call
   460 ms    6%    setAttribute
   474 ms    6%  PresShell::Paint

So we're spending most of our time evaluating JS, but only 6% of the total time is spent when the JS calls setAttribute() to set the path data. So in this case it looks like the slowness is simply the JavaScript engine being slower than Chrome's rather than the SVG path processing or painting being slow.

Comment 1

[Jan de Mooij [:jandem]]

That profile shows a bunch of time under fdlibm::asin -> fdlibm::sqrt, nursery GC, DoubleToString and math_sincos_impl. I'll take a look later this week.

Comment 2

[Jan de Mooij [:jandem]]

Can you still reproduce this with the latest Nightly? If I open this page on OS X, then start the Instruments profiler, then zoom in and out on the page, I see at least 15% of the time in painting/gfx code. There is definitely time in JS but not as bad as the numbers in comment 0.

Comment 3

[Jonathan Watt [:jwatt]]

With the mac build from:

https://ftp.mozilla.org/pub/firefox/nightly/2017/03/2017-03-23-03-02-03-mozilla-central/

and a new profile I get: https://perfht.ml/2mxSWyH

  7633 ms  100%  under load
  6908 ms   90%  JS::Call
   468 ms    6%    setAttribute
   546 ms    7%  PresShell::Paint

FWIW to zoom I'm using two finger scrolling with very a short, but rapid, up-down motion (so I'm not zooming in/out far, just enough to keep the resize script working hard for the duration of the profile - only 73ms worth of stacks in that last profile contain mach_msg_trap).

Comment 4

[mathieu.civel]

I also have very poor SVG zooming performance with both Firefox 53 and 55 nightly, on Mac. The zooming gesture is the same as the scroll one (2 fingers slide).

Tested on this page : https://bl.ocks.org/mbostock/4e3925cdc804db257a86fdef3a032a45

Profile : https://perfht.ml/2pEoSSy