Creating a sysimage for fast plotting with Plots.jl

A common complaint about Julia is that the "time to first plot" is a bit longer than desired. In this example, we will create a sysimage that is made to specifically improve this.

To get a reference, we measure the time it takes to create the first plot with the default sysimage:

julia> @time using Plots
  5.284989 seconds (5.22 M allocations: 308.954 MiB, 1.41% gc time)

julia> @time (p = plot(rand(5), rand(5)); display(p))
 13.769197 seconds (18.42 M allocations: 909.963 MiB, 1.75% gc time)

This is approximately 19 seconds from start of Julia to the first plot.

We now create a precompilation file with exactly this workload in precompile_plots.jl:

using Plots
p = plot(rand(5), rand(5))

The custom sysimage is then created as:

using PackageCompiler
create_sysimage(:Plots, sysimage_path="", precompile_execution_file="precompile_plots.jl")

If we now start Julia with the flag --sysimage and re-time our previous commands:

julia> @time using Plots
  0.000826 seconds (852 allocations: 42.125 KiB)

julia> @time (p = plot(rand(5), rand(5)); display(p))
  0.139642 seconds (468.42 k allocations: 12.176 MiB)

which is a sizeable speedup.

Note that since we have more stuff in our sysimage, Julia is slightly slower to start (0.04 seconds on this machine):

# Default sysimage
➜ time julia  -e ''
    0.13s user 0.08s system 88% cpu 0.232 total

# Custom sysimage
➜ time julia --sysimage -e ''
    0.17s user 0.10s system 94% cpu 0.284 total