CairoContext() is much slower than it used to be (macOS)

[cormullion]

This is more of an question than an issue, but I've been gradually coming to the conclusion that Cairo now takes much longer to "start up" (create a context) than it used to.

Here's an example on Julia version 0.6, running on a 10 year old computer:

               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0 (2017-06-19 13:05 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-apple-darwin13.4.0

julia> using Cairo

julia> @time cr = CairoRGBSurface(256, 256)
  0.015400 seconds (3.11 k allocations: 185.470 KiB)
Cairo.CairoSurface{UInt32}(Ptr{Void} @0x00007fee8c513930, 256.0, 256.0, #undef)

julia> @time c = CairoContext(cr)
  0.370006 seconds (2.55 k allocations: 142.626 KiB)
Cairo.CairoContext(Ptr{Void} @0x00007fee8b463600, Cairo.CairoSurface{UInt32}(Ptr{Void} @0x00007fee8c513930, 256.0, 256.0, #undef), Ptr{Void} @0x00007fee8b60f800)

and here's the time on Julia v1.0 for the same code.

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.0.2 (2018-11-08)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia-1.0> using Cairo

julia-1.0> @time cr = CairoRGBSurface(256, 256)
  0.104971 seconds (21.46 k allocations: 1.073 MiB)
Cairo.CairoSurfaceBase{UInt32}(Ptr{Nothing} @0x00007fdde2819aa0, 256.0, 256.0)

julia-1.0> @time c = CairoContext(cr)
 11.136036 seconds (9.58 k allocations: 534.713 KiB)
CairoContext(Ptr{Nothing} @0x00007fdde0844200, Cairo.CairoSurfaceBase{UInt32}(Ptr{Nothing} @0x00007fdde2819aa0, 256.0, 256.0), Ptr{Nothing} @0x00007fdde124e000)

That's 30 times slower on the computer that's probably 30 times faster. (I can't run Julia v1.0 on the old computer anymore, it's that old.)

So I'm wondering whether there's an obvious reason for the slowdown, and how to investigate the issue further.

[lobingera]

Here:

               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.0.2 (2018-11-08)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> using Cairo

julia> @time cr = CairoRGBSurface(256, 256)
  0.013114 seconds (21.46 k allocations: 1.073 MiB)
Cairo.CairoSurfaceBase{UInt32}(Ptr{Nothing} @0x0000000002c7ba60, 256.0, 256.0)

julia> @time c = CairoContext(cr)
  0.013396 seconds (9.58 k allocations: 534.775 KiB)
CairoContext(Ptr{Nothing} @0x0000000002d8c030, Cairo.CairoSurfaceBase{UInt32}(Ptr{Nothing} @0x0000000002c7ba60, 256.0, 256.0), Ptr{Nothing} @0x0000000002e12810)

[cormullion]

Blimey. Is that v0.5.6 on Linux? (I'm on v0.5.6 on macOS.)

[lobingera]

yes, that's linux and [159f3aea] Cairo v0.5.6+ [~/.julia/dev/Cairo]

[cormullion]

I'll ask for a few more data points...

[cormullion]

My current theory is that the number of fonts that are installed and active affects the start-up time for contexts. Some data points:

User	Platform	Julia	Cairo	Time1	Time2
cormullion	macOS	v0.6	v0.3.1	0.0154	0.370006
cormullion	macOS	v1.0.2	v0.5.6	0.104971	11.136036
cormullion	macOS	v1.1.0	v0.5.6	0.008384	10.546599
lobingera	Linux	v1.0.2	v0.5.6	0.013114	0.013396
pfitzseb	Linux	v1.0.3	v0.5.6	0.010506	0.00527
tobias.knopp	macOS	v1.1	v0.5.6	0.011026	0.570303
mkborregaard	macOS	v1.1	v0.5.6	0.285513	1.812419
goedman	macOS	v1.1	v0.5.6	0.00978	0.397401

The longer times here seem to be because these users have 'more than a few' fonts installed and active.

Probably no point in keeping this open!

[lobingera]

The cairocontext of an existing surface is internally more or less a copy of a pointer. The designers of Cairo.jl decided to add a pango layout here - which is needed if you want to use pango for text setting. So it might make sense to actually profile the full call to see if the time is spend in the first part (get contect) or second (create layout).